Why do some teachers allow students to go up en pointe if they're obviously not ready?

Well at my old studio that I just ended there was this one girl who was really bad. She's been dancing a long time but she's not strong at all and her technique is very weak (she doesnt point her toes, or straighten her knees, she's also a bit overweight not to mention that she doesn't even listen to corrections given by the teachers!). However one of the teachers (probably the best teacher at the studio) did not let her go en pointe but a different teacher did. So of course she went out and bought pointe shoes. And now she will most likely break her ankle or something. I however just got en pointe but a professional teacher at my new studio allowed me to because I have good enough tehnique to do so. Anyway, my point is that why would teachers just let someone en pointe with bad technique? I've seen this happen loads of times, why?