Plenty of us help, just not all the time, we have our own stuff to do too :p but either way we aren't obligated to do so. And in my case, and probably many others, we wont join in as a role we have little to no experience playing in that content. And healer/DPS spots get taken quickly :p
I never join clear parties though unless asked, it's basically a carry in disguise most of the time because once you know a bonus will show up those looking for a carry will try and ninja one too because there's no way of telling, which further ruins farm parties once those kinds of people have clears.
