This thread has gone from "why do guys wash out" to "why are guys kicked out?" I often marvel at just how hard it is to get booted from active duty, yet a few guys manage to do just that every year. My perspective is from 14 years active duty + 1 in ANG...all in the cockpit. If you read the AF times, you might get the vibes people get kicked out or sue the AF for reinstatement all the time. However, the average pilot type dudes are far enough to the right side of the bell curve to generally stay out of trouble. Here's the only rules I've seen where you get "fired" from the AF.
Rule one: Don't do drugs. Ever.
Rule two: Do not steal ANYTHING from work. Ever. No computer software, no pens, no office supplies, no airplane parts, no money (from Snack Bar). Nothing you can steal is worth more than A) your professional reputation and integrity and B) the money you'll make as an officer and pilot.
Rule three: Do not have sex with the help. Enlisted are 100% off limits. Some guys have pressed to test and survived. Some haven't. Don't push your luck to see where the coin falls when you get caught (and you will--nobody can ever keep a secret). That cute little airman you banged at the party last week is just dying to tell somebody she slept with a pilot. When you decide to go ahead, realize for the rest of your career, even into retirement, you are one bad phone call away from losing everything you have ever worked for.
Rule four: Communications/Security issues are important. Those kids fired for cameras violated security issues. Compromising air discipline by taking snapshots when told not to in a T-37 doesn't compromise national security. However...what if front line F-16 or F-22 pilots had snapshots of cockpit displays, etc. in their photo albums? If I can't trust you in tweets what makes me sure I can trust you when you are doing nuke certs in your B-52, B-2, or F-15E? Failing to take standard security issues will get you in Leavenworth under UCMJ or kicked out or both.
Rule five: Show up for work when told. That means...don't sneak off when not on leave status. Don't report late again and again and again. Anyone can oversleep one morning, but a pattern of "failling to show" is serious. Be where you are suppossed to be and where you told your supervisors you would be and you are covered.
Rule six: Tell the truth, even when it hurts. When cornered by the boss, fighter pilots boast they "deny, deny, and make false counter-accusations" but the reality is the smart guy simply comes clean and lets his boss make the right decision. Almost every fighter pilot I know has a story or two that ends with "...well boss, ....it seemed like the thing to do at the time". If they don't, then they likely haven't had very much fun on some TDYs. I've known guys to bounce back from some really crazy/dumb/really stupid/morally wrong actions once they bit the bullet and told the truth, but I haven't seen many that ever got caught lying bounce back.
What you might consider "showstoppers" aren't always....for instance...
DUIs are bad. People have survived them. Other guys haven't. Best rule of thumb is don't be the THIRD guy is a short while to get one. Idiot # 1 and idiot #2 sometimes skate, idiot #3 rarely does.
Been in a couple of squadrons where dude A has fling with dude B's wife. Personally, for a combat squadron, I think this is a much more serious offense than having sex with the enlisted support, and I think is almost the worst thing a military pilot can do to bring down morale in a squadron (the worst is cowardice or failing to execute duty during combat ops). However, AF takes a hard line on frat, but the "Romeos" I've seen have all gotten a "bad" assignment on their next round, but have managed to survive and continue careers.
Pretty much everything else is the same as the civilian world. The idea you cannot have sex with someone who wants to have sex with you simply because of some artificial (and some think antiquated) rules about fraternization clobber a few young guys (and some old ones) every year. Every once in a great while you find someone who you worked with/around is a liar/thief and gets caught doing something stupid. I've seen a few guys end up AWOL, but that has usually been to paperwork buffonery (failing to inform gaining unit when taking leave enroute, etc) instead of willful malice. I've know 2 fighter pilots who went off status for a 21 day alcohol detox....one survived and came back and another didn't (because he'd previously been treated and signed a sworn statement saying he'd NEVER drink alcohol again).
Its really not that hard....do the right thing, the first time, and when you make an honest mistake (which you will) good leaders generally back you up. If you are punished (grounded a week, letter of reprimand, etc) most of those things evaporate from your records quickly if it apparent there isn't a pattern of poor decisions and actions.
Go to UPT and concentrate on the basics. It can be, no kidding, 365 of the funnest days of your life.