It's usually no problem. It's always people going in the same general direction, sometimes to the same location. Or going to the hospital -- Dad's community is on land leased from the hospital. Cabbies always cut
through the hospital parking lot to save time getting there. At most it's a few blocks out of the way.
There are usually only 5 or 6 cabs waiting at the station so, without sharing, you'd have to wait if you're not one of the first people off the train. And unlike in places like NYC where they get one fare after another, they often have to wait quite some time between fares so allowing them to collect multiple fares at a time keeps the prices down.
And, for the first time in the 8 years I've been going, I did not tip.