As any New Yorker can tell you, our subway system is not just a means of transportation but a democratic lifeline that connects every part of the city -- rich and poor, east and west, professionals and students, hipster and inner-city -- closely with each other.

For sure, the lives the subways connect are often vastly different racially, economically and socially, but those lives are able to intersect precisely because the system exists. Without these wonderful underground trains, our diverse communities would be isolated from each other -- to everyone's loss. The system is also a great facilitator of commercial activity.

So given how important our subways are, why is our new Mayor allowing them to deteriorate?

The NYC subway system has come a long way. Compared to the rickety, graffiti-covered trains of the 1970s and 1980s, the new cars are upscale and clean, and crime is way down across the system. Riding the NYC subway is no longer the unpleasant and dangerous experience that it used to be. But to maintain the new standards, the system requires constant upkeep and an investment by the MTA and the city to keep its lifeline in good shape.

As a regular rider, I have noticed that the trains, especially those on the east side six line, have become noticeably dirtier. Floors are scuffed, doors and windows are grimy, seats are stained, and the whole car reeks, usually because of homeless people who practically live in the cars. I don't blame the homeless, but relocating them to shelters so that our subways remain clean for riders is the responsibility of the MTA and the city.

Then, of course, there is the lack of reliable service. I admire the system for carrying 8.5 million passengers per day and certainly don't expect perfection, but the reality can be pretty bad.

Most New Yorkers have experienced the frustration of waiting a long time for a train (even during normal hours), only to find it horrifically overcrowded when it arrives, having to squeeze onto the train (at the risk of life and limb) because the next one isn't coming anytime soon, only to then have it stop in the middle of a tunnel for several minutes due to "train traffic" ahead.

You don't have to be a mathematician to compute that when you have just waited 15 minutes for a train, the train in front must be at least 15 minutes away (at worst maybe 10 if it too was delayed because of traffic), obviating the need for your train to remain stuck in the middle of a tunnel for a long period of time.

And yet it happens -- a lot, and no one seems to know why. The MTA is constructing a new subway line on Second Avenue and there is plenty of other construction going on throughout the system, but what good is any of it if the trains themselves run erratically?

Another thing that never seems to get fixed is the elevator at the 63rd street and Lexington Avenue stop of the F train. This particular elevator is the chariot from hell. If it's not broken as it usually is, it takes longer to go down two levels than it would take to rappel there and is always filthy. The floor looks like a Jackson Pollock painting gone horribly wrong and the odor in there would make a rotten egg proud.

And yet no one ever seems to deem it worthy to replace this unreliable and disgusting elevator with a new one, or even bother to clean it up properly. Personally, I think the job requires boiling water, a truckload of antiseptic, more than a few pink slips at the MTA, and a recognition by de Blasio that the subway actually serves both his "cities," not just the Upper East Side.

People don't just go down to Wall Street on these trains -- they also commute back home in the evening to the Bronx, to Brooklyn, to Queens and everywhere else. In fact, a well-functioning subway system is essential to the social cause since it allows even the poorest living in the farthest reaches of New York boroughs to reach their place of work in Manhattan for a mere $2.50, without which their livelihoods would be even more limited.

Our new Mayor may mean well, but rousing speeches and poetic phrases don't a city administration make. Under Mayor Bloomberg this city improved and thrived, perhaps not in equal proportions for every group, but definitely overall. There were inevitable pockets of neglect and those should be fixed, but not at the expense of the basic foundation of the city, and that is something de Blasio does not seem to get.

From the snow removal debacle to his needless fight on charter schools, de Blasio is going about change the wrong way and in the process ignoring the essentials -- like our critical and immensely popular subway system. If this does not change, the Mayor's "two cities" will not even be a single city that works. Sanjay Sanghoee is a banker, author, and commentator. He has worked at leading banks and sits on the Board of a mid-market Hispanic radio station group. Follow him @sanghoee