Or indeed travel to/from places further along the route, including Old Trafford area, North Manchester, Oldham, Rochdale etc...
Or the easier access for services to elsewhere. I commute from East Didsbury to Media City each day, and it's piss easy changing trams at Cornbrook - out on one side of the platform straight over to the other side, and on the next tram within 5 minutes if that mostly. No schlepping halfway across Piccadilly Station, no having to wait 15 or 20 minutes for your connecting train etc...
Plus along the route there are places to change for trams to everywhere else on the network.
As for getting the bus, about 12-15 years ago before the tram came as far as East Didsbury I had a job in Trafford Bar. It used to take 2 buses and comfortably over an hour to do that journey. Now, even if I decided to walk down to the tram station (which I do actually) I could do the whole journey in 40 minutes comfortably.