Why do dentists keep asking me if I still have my wisdom teeth or not?

I was having my teeth cleaned and, as usual, I had to do X-rays. And as usual the dentist made reference to my wisdom teeth, but this time she specifically said something like "Seeing how we still have not taken them". This is the third dentist I have been to in the past 2,3 years, so I assume it is not any dentists in particular. Is any dentist supposed to take out my wisdom teeth or should I specifically ask any dentist to take them out?