They are still around, but far less than they use to be. I remember as a kid you would find a shoe shine guy setup in the lobby of most buildings fill with professionally dressed people.

Certainly work place attire has become more casual across the board, but there are still places where people dress up like lawyers. I find them still in train stations where there is a large enough traffic of people to support it. It goes to illustrate that fewer people are getting their shoes shined when a shoe shiner requires half the workforce in a city to pass them by instead of just occupants of a single building.

It is perhaps that shoes are simply more disposable than they were before.

We still have them in NYC. Right outside of Grand Central too (aka not the poor part of town).