And also they have much less capacity than mass transit systems like a subway, so they are bad for most commuters who tend to travel at rush hour[1]. I guess they are great in tourist areas though.
[1] In my experience, at least in the cities where I have lived
You could argue trams are more romantic. That is probably the major advantage.
I'd argue there are some limited places where classical trams on the road make sense, like some down town district. But you get almost the same utility with busses, passenger flow per lane is lower with busses, for a lot less money.
[1] In my experience, at least in the cities where I have lived