I prefer window, and I get window basically every time.

Airline "Southwest" allocates most seats based on when you click "check in". If you check in earlier, your boarding position is closer to first, and your chance of getting a desired seat goes way up. You can pay extra to board earlier ("Early bird") for $15. They don't have classes (there is no "first class" or business or coach) but you can pay for other features like cash-refundable tickets or boarding first.

Airline "Delta" simply lets you book your seat, so if you buy reasonable early, you can book a desired seat.

For other airlines, if the cost to upgrade to a window seat is on the order of $10-15, then I do it.

So I think your experience is limited to a small number of airlines, and your description of the OP as "childish" is poor.