thankfully nobody is forcing you to do fates. I'll tell you what... just because you see so many shouts for fate parties and fates disappear in a matter of seconds because everyone wants to do them does not mean you HAVE to do them. unlike popular believe, you CAN level pretty fast (if that is your goal) by doing chain grinding, too. just as repetative as fates but you can jump back and forth between both, I guess.

about the guildHESTs..
I haven't tried the lvl 40 ones yet, but I do notice an increase in difficulty up to lvl 35, so my guess would be that the hests are a means to slowly but steadily get people 'into it'. same as the dungeons only slowly become more difficult (some say haukke manor is the first difficult one, I personally found the first difficult one to be toto rak, and that's not even one you .have. to do for your main story so not everyone does it)