In dad's family, we usually waited until the elders got their food. Mostly because they were/are well into their 80s and 90s and can't really stand the strain of waiting in line for food. They'd get theirs, and if they wanted more of something, they'd ask whoever they were sitting with and someone else would go get it for them.
Mom's paternal family, kids always went first. It got them out of the way and into the other room. Then again, we didn't have a set meal time either, it was always more food being brought out or more family members showing up, so we didn't really have a line to get food either.
Mom's maternal family, everyone wants to be polite and wait for everyone else. I've learned that when they announce the food is ready and to help yourselves, I'm almost always one of the first ones through because someone has to be, and I don't mind being that first person through. Everyone in that family is more worried that everyone else should go first, they don't want to look greedy, etc. so they just wait. Besides, in that family, we always end up with about five times as much food as we need, so we don't have to worry about anything running out.
OP, it sounds like it's just different family dynamics. Nobody is "wrong" at all. If it really makes you uncomfortable to jump into the line at your DH's family gatherings, then wait a bit. It's still not wrong to do that. He can take the lead in your family, but if you're really not comfortable elbowing in to the front then don't. As long as nobody's offended by you waiting, it shouldn't be a problem at all.