if I'm not mistaken, early primedice also change seed on every roll but not anymore
now afaik primedice and just-dice only change server seed on (player) demand
To be honest I think there might be good reasons that the other sites haven't changed but I'm not really an expert in that field. It could be more about a matter of opinion as to which system is fairer. If you're concerned I'd suggest PMing wetsuit and having a chat about it. I know he hasn't logged on to the forum for a while, he's been away but should be back very soon. I think me getting in the middle of the debate would probably only confuse things.