Depends on the vehicle. My 93 Silverado is a mess because it gets winter driving duty, and it has 200K miles on it so I don't care. My Cobalt is the random cruiser and I have a camping chair for after softball games, along with my baseball...well softball now, glove. etc. I have a bunch of random shit on the front seat like receipts, some change, etc. I clean that up every once and awhile, but usually don't care.
My Vette on the other hand, is spotless. I hate when people don't shut the doors the right way (placing more than 1 finger anywhere other than the rubber seal at the bottom of the window and gently pushing it shut). Nothing extra is ever left inside of it. I keep my sunglasses in the middle console. I even have all of the vents lined up with each other instead of all in random directions. Lol, never realized I was so strict on it until listing it all out. I don't plan on changing though! 🙂