That still doesn't make the A ranks "not content", it just makes them less exciting content. To you at least.

There are people who dedicate large chunks of their playtime to searching them out and organising hunt trains. It's certainly engaging to them.

Flying around in the zone searching it is still time spent in the game, out in the field, enjoying the scenery and music.

Weather changes are what make rare FATEs extra special - it hardly happens so it's exciting when it does. If it happened more frequently with every semi-rare monster I think we'd get tired of it.