I think it depends upon where you live in more ways than one, as to whether they will be widely available or not. I'm sure some of it is related to socio-economics, though.
Where I used to live, I'd have been really surprised to find an apartment that didn't include its own washer and dryer (that was part of the apartment the same way the kitchen appliances were). Where I live now, I'm really surprised when I see places for rent that do include a washer and dryer in the actual residence. It's slightly less rare to find places that have a W/D hookup (so that you can provide the actual appliances), but even that is nothing like guaranteed.
Most of the places that do include a W/D here are either ridiculously expensive for the area, single-family detached houses for rent, or both.
So, obviously, laundromats are much more common here than they were in the previous city I lived in. Apartment complexes with coin-operated laundry rooms are also much more common.
I don't know what causes the difference, although the city I live in now is very much a college town, and the city I moved from very much was not. I count myself fortunate that I live in an apartment with both W/D hookups in each unit, and a conveniently-located coin-operated laundry room. Since the washer/dryer combo unit I have is not especially good at large loads, or at drying anything, it's nice to be able to use industrial-size dryers when we need to wash our towels (so that they will dry in some period of time less than 4-5 hours). But it's also nice that we don't have to schlepp all of our laundry to an outside facility (even if it is 20 feet from our front door).