Isnt the ARC fee's every year a bit of a pain.
Isn't
every fee, by definition, a pain in the proverbial?

Seriously, it all comes down to whether operating within the requirements of a managed environment is too much of a hassle, making the yearly renewal the most attractive option. I guess also many owners would feel a bit uneasy about having their aircraft inspected by qualified personnel only once every three years.
I wouldn't be happy with it myself and prefer to have it fully inspected every year, like I've always done before the whole CAMO thingy started, and I only fly a relatively simple self-launcher.
Ciao,
Dg800