In vanilla, the slow rof autos ruled. Sometimes mid rof. High rof autos were not very good at the time. Autos in general became garbage around dark below when they nerfed the crap outta them and they went unused for a long time. The 2.0 update just before TTK knocked hand cannons down and brought autos back to a reasonable place. Naturally people went back to their old favorites and were drawn to the slow and mid rof autos. They are able to hold their own now. That and there are only a few high rof autos out there now. Most people didn't hold onto random legendary ones. Some still had aetheon's epilogue or nechrochasm. The only year 2 high rof autos are the doctrine and the Arminius. Took a while for anyone to give doctrine a chance and it had to be gotten from trials. As for Arminius, nobody wanted to order a high rof auto from the gunsmith and then it's only available now and then. Plus, both are very dependant on getting the right roll. Purely based off that, it took a long time for anyone to really discover how good the high rof autos are now.