Is the back seat the de facto protocol? I always sat in the front. It somehow feels more friendly and personal. But in a taxi, I'll usually sit in the back.
Lyft started out with sitting in the front as the standard protocol (which is no longer the case), but AFAIK UberX has always been back-seat & taxi-like.
I moved coasts and city sizes, riding uberX a lot in both. East coast big city was strictly back seat. Continued the practice west coast smaller town and had a couple drivers mention it was unusual when I asked.
The front has the airbag. Nothing personal, but I'll be up there.