Time vs money for me. I can drop it all off, get some things done, grab it on the way back home. Spend the $50 ( and whatever my tire and tube is) an be done is how I roll. lol.
I just slap it on the bike, and I'm ready to ride. Why not have them slap a tire and tube on while they got it. I pay the little extra, and just get it done. So I'm not wasting time doing it myself. I live in a big city, plenty of people to do whatever ya want if you ain't got the time, or they can do it for less than what you feel your time is worth.