That's another thing that baffles me sometimes--dithering. This happens to me a lot when I'm playing DDO and I say to the guild "I'm going to run X, would anyone like to come?" A large percentage of the time, nobody says anything, which is fine. Sometimes someone will say "sure, party invite". But more often, I get some sort of weird halfway response like "eh, maybe". They then switch characters, go get a cup of coffee, read a novel, stretch, and then 20 minutes later I get a message saying "so, are you going to invite me for X or not?" to which I reply "I'm already done."
Of course, then there are the people who join you for X activity and then immediately ask if you can do Y instead. This activity hijacking is also baffling to me, but from what I can tell it's the result of people who can neither lead nor follow. They can't do things by themselves--they need or imagine they need someone to hold their hand--but they categorically refuse to put their own group together to get it done. Apparently they think the LFM (looking for more) panel has some sort of voodoo curse and if they ever put up a group they will be struck by lightning. Yet if you do bring them into the group they don't follow instructions, don't cooperate with the group, and basically contribute nothing. This is probably why they believe in the LFM voodoo curse--every time they try to build a group it falls apart because they can neither give instructions nor follow them. So the only option they're left with is to glom onto someone who is both competent and amiable. I'm not particularly amiable. If I advertise for help doing X, then I'm doing X. If you want to do Y, form your own group.
I wonder if that's really all it boils down to--people not being clear in their own minds about authority, responsibility, or leadership. You can't be decisive or get anything done if you don't know whether you're asking someone or telling them.