Although there are some that reserve the "best" seats for their own frequent flyers, which is almost as irritating
Why is that irritating?
If I book a ticket with an airline I don't often use, I accept that they will reward their FQTVs by giving them a good seat, after all those travellers provide regular income for the airline and a little sweetener helps to retain their business.
On other airlines I get the same benefit.
Infrequent travellers still get seats allocated.
Seems fair enough to me.