Why does TMobile believe it a good thing to have a customer on the line for 2+ hours for basic support?

I have never, and I mean never, had to wait on the phone or even on their chat for as long as I have had to do for T-Mobile. I had a billing problem, and it took over 1 hour+ on hold, then another 90 minutes with 'support' just for the rep to completely screw up my account, never call me back like they promised, then needing to get with someone else a few days later just to get THAT rectified, now my phone can't even receive calls. This is completely ridiculous. I am an unfortunate Sprint port, and I could never have imagined that the customer service would be so awful. I am seriously considering switching and I was a Sprint customer for over 15 years.