I don’t have any data to back this up, but I think window and aisle seats being more valuable doesn’t necessarily mean they can be sold for more.

I am very tall and I always pay for a seat with extra legroom in economy. Whenever I’m picking my seat early, almost every seat in economy is available. People could pay to reserve a window or aisle seat, but anecdotally it seems like almost no one does this. Everyone I know just tries to check in as early as possible so they can grab a good seat before they’re all taken.

I don’t think airlines are actually losing any money by seating families together. It’s not like all those window and aisle seats would have been paid for otherwise.