Earlier quoted context omitted.
A lot of tram systems don't have dedicated rights-of-way.
Still they don't/can't break as abruptly as buses and the ride is a lot less bumpy in general. And buses are notoriously crammed, even when the next bus would supposedly be there in 2 minutes, people will squeeze into the one that's there now, with trams you can just attach another cart, and carts can be larger to begin with.
Ah, at least in Toronto, we tend to see our trams as streetcars rather than trains, so they fall victim to the same "next bus" problem you quote above. More so, as trains can't hop over one another to pick up passengers at alternating stops, a practice common with the busiest of routes. That said, streetcar drivers are often much calmer than bus drivers. There's just a different kind of expectation...