Making OS3.x better only hurts OS4 sales.
Seeing that OS3.x runs on real Amigas with 680x0 CPUs and only OS4.0 runs on PPC enhanced Amigas, I don't think this statement is entirely true. I can't justify the cost of a PPC accelerator for my 1200 or 4000 and have no interest in the newer pseudo-Amigas needed for OS4.1 so... I'll never be using OS4.x so there's no competition for people like me who see Amigas just as a retro hobby and use more mainstream modern machines and OSes for regular everyday computing.