I don't think people are patient enough today to allow a coach several years to work through problems. You can look all across the country and see university presidents, athletic directors, boosters, and fans, who all have a "win now" mentality. Fewer and fewer people are willing to wait extended periods of time for success, especially when they see coaches take new jobs and have immediate success. You look at Michigan, who fired Rich Rodriguez after four mediocre years, hire a new coach, and win a BCS game. You look at Alabama, who went 6-6, 10-2, and 6-7, before hiring Nick Saban, who went 7-6, 12-2, and then won a championship. Lane Kiffin gets hired at USC and, after a few tough years with NCAA penalties, has them poised for a championship this next season with a loaded roster.
If you look across the college football smorgasborg, you see teams making good hires and having immediate success, and that's what people want, that's what people desire most. They want a bombshell hire who will take them places now - not tomorrow, not next week - now. Not everybody has that immediate success and ends up firing their coach (see Charlie Weis), but who cares? People would rather go through a couple of coaches in a decade to find the winning one than allow a coach a decade or more to bring the team to prominence. OP, you've been around since the late 60's through the Tom Osborne era. Think to yourself now - how many people would give Bo Pelini, say, 23 years to win a championship, like we gave Osborne? Heck, it took Osborne 11 years just to get to the game, which he lost, and didn't return to for over a decade.
It's little more than selfishness spawned by the often-lawded brilliance of great coaching hires and immediate success.