I am fortunate that not only do I tank for our primary group, I am in almost all alt or secondary groups also due to a lack of tanks and heals and my raid explanations. I am there whenever asked and usually pass drops I win to mains in secondary runs even when the alt in that run can really use the item. I would be there even if I wasn't allowed to roll for drops on alts to help the guild. I sympathize with those not in a consistent raid group or one that has a harder time downing bosses.
That being said...if my main did not get opportunities to raid AND I wasn't allowed to roll for loot for my class, I wouldn't come and wouldn't blame anyone else who didn't. In fact, I doubt I could stay in a guild that did that to me. I don't know that I could stay in a guild that I observed doing that to another guildie.
I am good enough to down bosses with you but cannot be rewarded unless it's someone's hand-me-down? No thanks.
"he doens't need healing, he doesn't need healing, he doesn't nee-WHAOSHIT!wtf was that man!". Please stop leaning on TDR. -Teng