Basic human psychology: You accept a certain risk level to get a reward. Familiarization with the danger (you've been skiing many times and nothing happens) means you feel the danger as less threathening - it becomes an abstract or immaginary thing, you think about it but there are no feelings of danger. On the other hand, skiing in powder feels really awesome. Do the math...

The only known remedy is education and training, but that gives no warranty, just better decision making tools.

Despite best efforts and really skilled personell there is - and always will be - a certain random factor in avalanches.