All of those things + winning and what you're ceiling is at a particular program also has a lot to do with it. In regards to coaches that have traded out for admin jobs- @ChiefSmoke can add to this, also, but I know of several former head coaches who have gotten into admin and it's not that the hours are actually better....however, you're at least getting COMPENSATED much better for your time than coaching.
Admin base stipends, across all levels/ranks (elementary-high school) are almost always as good as HFC stipends (in the very least) & the majority of the time SIGNIFICANTLY better. Then, throw in the massive amount of extended days? The switch becomes a financial no brainer.
You can be up there in June or July for hours during the week as a coach (some places have extended days, but if they do, it's few and your base coaching stipend isn't as high) working for "free" essentially or be up there as an admin, actually getting paid for it.
Coach brought up another good point as well about certain household, blue blood programs.....those jobs rarely come open. "Everything" (as relative as a term as it can be to the coaching world) is there....from the pay, community/administrative support, "football town" mentality and then...let's call it what it is, too...the chance to WIN. Coaching is about relationships (and, so many other hats that coaches have always worn..moreso now than ever today), yes...but, it's also about WINNING.
THAT is one of the few reasons as to why you just don't see certain jobs come open often. On the flip side of that, there is a reason you see countless others have turnover like they do......take the LACK of the aforementioned keys to having success, add that to a low talent base year in year out where "said coach(es)" can probably tell you the outcome (+/- a game here or there & not in a good way) of their season(s) more years than not on the first day of January workouts for the upcoming year? And you get turnover....
1- Pay for the time is garbage.
2- Lack of administrative support from where it matters from everything to budget, facility upgrades, teaching position(s)/in school strength/conditioning.
3- Staring down the barrel at the talent you have to face every year in districts that have other aspects above also going for them?
4- See ya, bye.