If the company says you get unlimited pto, and actually delivers on it's promise, why couldn't you just take off for like 6 months every year? If you actually need to get approval for time off, then it's not 'unlimited', because they are literally 'limiting' your pto. Is there anything to these 'unlimited pto' offers, besides being an obvious scam?

I don't think they're usually a scam. Typically, small startup (which may have quickly grown into a larger one) with idealistic founders who fancy themselves as being forward thinking and pro work/life balance and think that an unlimited PTO policy will allow employees to take care of themselves. Likely they at some point worked somewhere with a very strict policy and saw bad things happen to people who had medical problems, family emergencies, etc. and don't want to subject their employees to that. The reality of course being that nothing is truly "unlimited" and instead there's an unspoken limit that you don't want to cross (because it will affect your performance reviews whether it's mentioned or not) and the fear of accidentally doing so means that people take less time than they otherwise might. Then of course, because people look at how much time their coworkers take off to figure out what the "norm" is and stay on the safe side of that, the "norm" edges even further down over time and eventually no one ever takes time off unless it's a true emergency. So generally, I think their heart is in the right place; they just didn't fully think through the systemic effects. Or who knows, maybe by now some truly unscrupulous execs have figured it out and are actually doing it on purpose...