Three things seem pretty clear at this point in history:

Self-driving cars will begin coming to market before long.

They'll generate huge profits for some companies.

Google has been a leader in developing self-driving technology.

But does it follow that Google's parent, Alphabet (NASDAQ:GOOG) (NASDAQ:GOOGL), will reap the rewards of its technological leadership? Or put another way, are the potential profits from self-driving cars a reason to add Alphabet's stock to your portfolio?

A lot of commentators seem to think so, but I'm very skeptical. Here's why.

Alphabet has what looks like a leadership position...

Google began tinkering with self-driving cars way back in 2009, long before many investors began taking the technology seriously. The original team behind what became knows as the Google Self-Driving Car Project included several robotics all-stars who seemed ready to invent the future. The whole thing appeared to be decades beyond what the established automakers were doing.

For a while, it was. Of course, in the last few years, some automakers and auto-industry suppliers have invested heavily in the technology and made significant gains. But even so, Alphabet's self-driving unit, which was spun out of Google and renamed Waymo late last year, retains some big advantages:

By at least one measure -- "disengagements," the number of times a human driver has to take control of a self-driving test car -- Waymo made major progress last year and appears to be ahead of most known rivals.

Maps. The first self-driving cars to come to market will rely heavily on highly detailed maps as a backup to their sensors. Google has been mapping the world in ever-increasing detail for years; Waymo will have access to those maps, while its competitors will have to look elsewhere.

Waymo has developed its own self-driving sensor hardware, including -- crucially -- LIDAR units that cost much less than current commercially available units.

Those are significant advantages. But there's a big question that might not be obvious to investors who don't have a deep understanding of the auto industry:

How will Waymo bring all of that to market?

...but bringing it to market may prove complicated

Waymo's CEO, John Krafcik, is a respected auto-industry veteran who was hired to lead the project in September 2015. Krafcik brought a welcome dose of realistic transparency to the project when he made it clear that Alphabet has no intention of manufacturing its own vehicles. Instead, he said, Waymo would seek to bring its technology to market via partnerships with established automakers.

There's just one problem: The automakers aren't exactly beating down Krafcik's door. In fact, the auto executives I've talked with feel that they have very good reasons to steer clear of a deal with Waymo, starting with control of the data generated by self-driving cars.

It's almost an understatement to say that automakers are very aware of the smartphone precedent. The phone makers that chose to adopt the Android operating system ended up making hardware on very slim margins. Alphabet ended up with most of the profits, because Android provided it with the (immensely valuable) users' data.

Auto executives don't want to end up in the same boat, and they know that they'll soon have alternatives that will allow them to keep at least some control of the data. At least one alternative, a partnership between Delphi Automotive (NYSE:DLPH), Intel (NASDAQ:INTC), and Mobileye (NYSE:MBLY), aims to have a self-driving system available to any automaker that wants it by the end of 2019. That partnership will allow automakers to retain much of the data, and auto executives see it as homegrown -- created largely by established industry suppliers, not by Silicon Valley hotshots.

Given that, why go with Waymo?

That said, a couple of big automakers have kicked the tires on Waymo's technology:

Fiat Chrysler Automobiles NYSE:FCAU) the latest vehicles for Waymo's test fleet, based on the well-regarded Chrysler Pacifica minivan -- but there's no sign that the two will move forward on anything that could lead to a product for sale.

Honda NYSE:HMC) prodding other potential partners to take action. But at least as of right now, it's not clear exactly what was going on there.)

Waymo may well find a profitable line of business in selling its sensors to other companies. And it's likely that some automaker, somewhere, will eventually give its self-driving system a try.

But unless other research and development efforts hit roadblocks that Waymo is somehow able to skirt, it seems unlikely that it will be a dominant player in self-driving systems anytime in the near future.

The upshot: Don't buy Alphabet just for self-driving

There are plenty of good reasons to consider adding Alphabet to your portfolio. But if you're looking for a targeted self-driving investment, Alphabet probably isn't it: As of right now, it's not clear that Waymo will ever add much to the search giant's bottom line.