Opportunity cost. By having to study it at all, those students lose the opportunity to study something else that might have more value or merit to them personally. In that way, it definitely is a forced priority.

The Welsh language isn't part of the cultural identity of most English-speakers in Wales. That's why they find it annoying when their children are forced to learn it. It's like forcing every child in Brittany to learn Breton when most of the population speaks French and has no desire to speak Breton.