One factor is simply the number of posts from users combined with somebody actually knowing the answer to your specific question. If it is a heavily posted forum and somebody is not around who knows the answer to your question, your post can scroll off the first page pretty quickly.
It does seem to me there are more contributors around these days, but there are also more forums (note the plethora of i-gadgets) so I think we're still spread thinly.
Pplease keep in mind we are all volunteers. Once I start helping somebody I do feel a kind of Chinese obligation to follow through as much as I can, but it is difficult to tell my wife I am sorry I cannot come to supper right now because I am helping somebody who forgot to back up their iTunes folder (EMERGENCY! URGENT!!!!) get their computer ready for a party tonight. 🙂
Also, remember some of us may not even know what it is you are asking ("Mission Control"??? - check my profile below 😉).