It's the same as always: LFG is not all roses. Unlike matchmaking, it takes effort and time. It requires active socialisation, and some players are not social. You have to be prepared to get into the shitty group and be kicked in the end, 'cause that happens too. And some people like me just have negative preconceptions about LFG from previous experience, and will rather go play something else instead. For many people friends and clans were the gateway to raids and trials and other end game activities. Look around: "my friends don't play anymore" is one of the top topics. There are more solo players now than was at the start of D2 because of that. And now they are artificially slowed in their progression.