It also means that you'll be replacing your crew constantly, making everyone a novice in every flight.
Which is a non-issue if we're sending people up for other reasons than to get astronaut training. If we're sending a geologist up to study a comet, then it doesn't matter that he's a novice at astronauting.
Also, exactly why do you think we do manned flights at all? It's precisely to increase the safety to the point where you can sell tourist tickets to celebrities
That may be your reasoning, but there are other lines of reasoning too, that don't require increased safety. For example, sending people up to do construction work on comets. That doesn't require increasing safety to massively redundant levels.
At a 25% level (or pick any other number, really, that you can agree with -- the point is reduced safety from current, not the exact 25% number) if you need 10 geologists up there, you send up 40. If you need 100 construction workers to build a moonbase, send 400. With a different safety percentage the numbers will be different, but the point is we don't need to be absolutely sure that if we send n people, then n people reach the destination. That's just an added excessive cost, and we can do it for cheaper if we accept some losses.