I only wish it's that simple.
I've personally joined many runs where players need help on pulls and I've happily passed items over. Even if it's a Reaper and/or Mythic bonus item. And even if it's an item I could have used.
Of the last year or so however, I do this less and less.
Not because I dislike doing so, but more because in my experience players don't remember who helped them before - and thus when I make mention I can use stuff (just the basic item, not even with any bonus), it still seems to go into their own packs or to someone elses packs, never mine who basically helped them gear up half of their current toon.
And in some cases, loot envy even kicks in and then you wonder why bother in the first place just to get harrased afterwards? Passed a raid item over to someone who had basically ransacked (can confirm this as we saw their Raid LFM's turn up many times) their toon forgot about them being on the ransack run at that point with us and was praying that someone would have it drop and have a chance on a roll on it. I had said if I had it drop I'd pass it over if no one else says they'd want a shot at it also.
No one said anything.
I was the last one to loot chest and said item dropped. Laughed, told them it was fate, and gave the item over to them. THEN I get tells from someone else saying - Shouldn't loot "I" don't use be put up for roll? And as mentioned, it wasn't like I didn't even give anyone else a chance, I typed it out plain as day in chat if anyone else wants they'll need to say something now or I'm just passing it to the Raid Leader who wanted said item.
Then there's the story that matters most to this thread: A long time ago, before Monks could break material DR, a pair of named Handwraps were made (Devout Handwraps) and would drop in the Shadow Crypt optional. But their drop rate was silly low and thus players that were able to run it asked others to help pull. Now, as said, the rarity was silly low, so pretty much no one on ANY server had a set yet at that point. So I saw that they were going to farm it and joined to give them a hand, if only to help them get it first on any server (just seeing the darn things turn up would have been a satisfying outcome for me).
Here's the thing, those HW were BTC, meaning you only ever need one to drop for your character. But it's absolutely possible with RNG being the way it is, for more than one to drop. Then anyone else who could use them could also benefit from that run's second pair drop, etc. I've seen this happen many times before.
But alas, the members of that run saw that I was on my monk and asked if I had the wraps already? I said no. Got booted before I could even follow up to say I was there to help them get the first drop on any server first and foremost - and only have a chance at a spare set if a spare dropped.
Oh well.
I still managed to get my pair before they did in the end though...
But, back to this thread. Yeah, definitely should join - to help someone gear up if not possibly have yours drop too. But lots of socio-gaming hurdles to keep track of and if you're not happy with handling those hurdles, then don't join.
J1NG