I hate to break it to those of you who have the misfortune of living in one of these metropolises where demand is outstripping supply, but that's not the situation everywhere. Courses are in reasonably plentiful supply in many areas.
"You and your group"? That's the problem, sometimes there isn't a group. Sometimes we just want to play a few holes at lunchtime. Sometimes we want to throw two off the tee or putt three times. Sometimes you meet your buddy in the parking lot and decide to throw some holes together. Establishing tee times would inhibit these informal practices. Practices, that while annoying and rude when every hole is packed, are essential to getting people to learn the game on their own time and by their own means.
Had I been introduced to disc golf in an area where courses are packed and I couldn't play in an informal manner, I would not have gotten hooked, and I suspect that goes for a lot of folks.