I'll bet my next weeks wages that those who don't join for whatever reason will wish they had done if the ever find themselves down at CAA towers facing an investigation into an airspace infringement or other misdemeanour.
That's why I joined, and remain a member. The mag's good, but I really have too many aviation mags anyway. And it's possible that the legal stuff may not be all it's cracked up to be. But if I ever get investigated by the CAA, and am wondering what to do, it'll be good to know where to start, and to have someone on my side. That's worth the subscription to me.