Just a query on Tanks running before all trash is cleared

I hope this doesn't sound too much like a complaint, I'm just trying to understand as I can't see the reasoning behind it. It seems to be becoming more and more common for tanks to pull, for example, 2 groups of trash, dps begin to burn them down, then the tank runs to the next group before all enemies have been dealt with. Quite often during this, buffs and procs are falling off and it's amazing how often I've seen the tank even run into locked doors that won't open until all trash has been cleaned. I guess my question here is why? Is there a advantage to this? A dps gain I'm not seeing?

To keep it brief: No, they are just bad.

They believe they'll get faster runs. But it just annoys DPS and puts extra strain on healers.

It's definitely annoying, though I've seen both healers and DPS do it as well. It's not a type of stupidity exclusive to tanks, unfortunately.

Yeah I keep seeing more people do this recently, and I don't know why.
I've heard some say they wanna finish their AOE combo. As a tank main I can assure everyone that isn't needed.

Thank you all for the fast replies :) I was thinking this was the case but I thought I would ask incase I was missing something.

Canadane exactly, as a Samurai I often lose jinpu and shifu when tanks do this and I always hear a very loud sigh from my friend who plays Dragoon as his life of the dragon falls off XD

Maybe they think if they do that they are helping by keeping u dpsing constantly where ur buffs dont fall off between pulls. Not saying its right ir wrong and i dont know if thats the reason but sounds good lol.

Are the tanks leaving to pull when enemies are at 30% HP or lower or is it happening when they have high health. If it's the former, it is pulling behavior WoW tanks talk about doing in the other forums. They don't have walls to stop people from pulling up to the boss or instance, so some try to run ahead before the DPS can do the pulling for them. If it's the latter, not sure. They could be trying to do 2 AoE combos not trusting the DPS to cool their jets. Not saying that is right since it annoys me too with me saying, "Make up your mind." I can understand using an AoE or 2 running through, but it wastes cooldowns to only park for 10 seconds, then drag.

I flippin' hate it when tanks do that. Give my mana and brain a couple extra ticks before you mindlessly pull the next crowd pls. I will do my best to heal you on big pulls, but give my poor head a break of a few seconds every minute please!