True enough, even the big ones go bust taking all the cash with them.
I usually refer to the "big 3" and they certainly haven't! You erroneously mentioned "PTC" which I have never considered in this category. However yes, just as plenty of "modular" FTO's have failed, any business can go bust. They normally do so because they run out of cash, not because they take it with them. The obituries of failed companies, including airlines, makes for a very long list.
Risk is unavoidable, but there are simple steps that minimize it. Unfortunetaly too many people are driven or pursuaded to take the "cheaper" options by others who often see any other route than their own as a threat. For many, their choices are limited by their own economic necessities. Thus, people will make their own choices based on their own circumstances, and what they can afford.
Suggesting that it is a level playing people, or that the same options are as likely no matter what route is taken, is simply wrong advice. I don't give it. A lot of people come here to advise people that the route to their goal is the one that they themselves still haven't fully achieved, but are still hoping to. It makes absolutely no difference to me, what people decide. I simply state the realities that exist at this end of the marketplace. It is a tool for those considering their options to use as they see fit. Ignore it with pleasure.