The MacBook Pro's new Touch Bar. Apple With its new Surface Studio desktop PC, unveiled last week, Microsoft did something unimaginable: It upstaged Apple.

The machine's sharp, superthin screen, smart design, and innovative click wheel led Business Insider's Steve Kovach to write that "the Studio isn't a computer. It's an entirely new computing category, a sort of desktop-tablet hybrid that already has people excited."

When Apple gathered tech reporters in Cupertino, California, on Thursday, the company showed off a new lineup of MacBook Pro laptops sporting largely the same design we've seen for years, but with the addition of a new touch-screen Touch Bar that doubles as a Touch ID fingerprint sensor.

The contrast between the cool new Surface Studio and the so-so MacBook Pro was striking. Microsoft — popularly known for decades as the bland purveyor of bland software for bland beige boxes that sit in bland offices — is out-innovating the company that once dared its customers to "Think Different."

The Microsoft Surface Studio. Microsoft

And with Microsoft making such a splash with the exquisite Surface Pro tablet, Surface Book laptop, and now the Surface Studio PC, it has Apple's legions of Mac devotees asking: Why can't Apple just build a better Mac?

Well, those Mac fans ain't gonna like the answer. You see, the replacement for the Mac is already here. It's called the iPhone. Maybe you've heard of it?

Stalling for time

Apple is the most valuable company in the world, and it's all thanks to the iPhone. Sure, Android phones dominate by market share. But at the end of 2015, the iPhone was more profitable than all the major Android manufacturers combined.

Plus, the iPhone drives Apple's growing services business, including Apple Music, iCloud storage, and, most of all, the 30% cut it takes of all App Store transactions.

Ultimately, as the iPhone grows, the Mac's importance to Apple diminishes. Check out the steady year-on-year revenue decline of the Mac since 2011:

Sure, Apple could pour money into the Mac business, inventing a touch-screen MacBook that rivals the Surface Book. With Apple's cash reserves, the sky's the limit.

But Apple's actions aren't about money or beating Microsoft on the PC battlefield. Apple will never admit it, but the real goal is to ensure that the Mac stays frozen in time.

Pressing pause

While you and I might want a touch-screen Mac, Apple has already moved its big-picture focus to the iPhone and iPad. Launching a touch-screen Mac now has a huge potential to confuse the market, split the developer base, and pause the overall transition while customers try to figure out if they need a work-friendly iPad Pro or a touch-screen-enabled Mac.

It's unarguable that today, it's difficult for most people, particularly students and creative professionals, to do their entire jobs on an iPhone or iPad.

Consider this, though: What can you do with the iPhone today that you couldn't when it launched in 2007?

When the Apple App Store launched, stuff like Google Docs on the iPhone seemed like a convenient novelty; now, as the apps have improved and their feature lists have filled out, they've become normal parts of the workday for millions of people.

Apple iPad Pro. Apple

It'll be a while before iOS, the operating system on the iPhone and iPad, is really, truly ready to replace a Mac (or a Windows computer, for that matter). But we've already seen signals that Apple is thinking in that direction: CEO Tim Cook probably tipped his hand when he pitched the giant-sized iPad Pro as a laptop replacement.

So while the world waits for iOS to mature, Apple still needs to keep the Mac around for the many millions for whom an iPad still isn't good enough. It's a tricky balance — if Apple makes the Mac too modern, it hurts iPad adoption. Not modern enough, and Apple's install base erodes away before there's a real replacement.

And when Apple finally starts to push into new platforms like augmented reality or even audible computing, you can bet that it will be centered on the iPhone, not the Mac.

Hence, we get things like the Touch Bar — an underwhelming compromise between old and new while the future shakes itself out.

Microsoft swoops in

For Microsoft, this is a huge opportunity.

Microsoft lost out on smartphones — by year's end, Windows phone platforms are expected to drop to a pitiful 1% of global market share. And with overall PC sales shrinking and smartphones handling an ever larger amount of everyday computing, the future of the company's Windows business is in danger.

Windows 10 is designed to meet this threat head-on: It's designed to bridge the old Windows desktop experience with a new, touch-friendly interface. It tries to be as good for tablets as it is for PCs, and for the most part, it succeeds. Where Apple is trying to balance an old platform and a new one, Microsoft has one very mature operating system.

So with Apple stuck in this weird stage between Mac and iPad, it's the perfect time for Microsoft to get people jazzed up about Windows 10. That's where the Surface line comes in, making the case to consumers that Microsoft is really good at helping you get stuff done and at coming up with nifty new touch-screen experiences.

Microsoft Surface Book. Melia Robinson/Business Insider

Clearly, Microsoft would love if everybody on the planet bought all Surface everything. But even if they don't — the devices are pretty expensive — Microsoft's real end-game with devices like the Surface is showing off what their hardware teams can do that Apple can't or won't.

The mere fact that we're talking about the real possibility that Microsoft out-innovated Apple is proof enough that the strategy is working. It's going to get people at least considering a Windows machine, even if it's not a Surface, whereas before they might have just bought another MacBook.

The real game now is whether Microsoft can use the Surface hype to bring Windows back to growth — before Apple sorts out the existential crisis with its platforms and starts pushing its computers forward again.