As others have said, aggro is so easy now that there is no reason to sweat someone getting ahead of a tank in normal dungeons.
I can see healers, or maybe the other dps, feeling upset by a dps early pull throwing a wrench in their plans, but as a tank our rotations are always fairly simple and we can pretty much grab aggro spamming any button with our (zero penalty) tank stance on.
Gone are the days when an early pull might force a tank to fall behind their rotation/opener as they desperately spam Overpower or some other one-button enmity move to catch up.

Many tanks see themselves as the de facto 'leaders' of the party. As a tank main, the way I see it is this:

If people are running ahead of me, that means I'm not running fast enough. If people wanna go all out, I should be ready to go all out.
If I'm not ready to go as hard as the other people on my team, what right do I have to say I am leading it?

Our job as tanks is to hold aggro and help kill everything as quickly as possible while making the healer's job as consistent/predictable as possible. That means being ready to be the first one to die. If someone dies before me because they have aggro on something, I've done something wrong. To deliberately let someone keep aggro and die is a complete abandonment of our responsibilities as a tank.

If you want to be the leader, you need to lead. Do your job, or someone else is gonna do it for you.
If you want to be a tank, you need to tank. Do your job, or someone else is gonna do it for you.

Being a leader is a responsibility, not a right. It's about taking care of your teammates and doing everything you can to make the team successful, not having things go exactly the way you think they should.
If someone pulls more than you did, they are saying they think you guys can handle it. They may be right, they may be wrong, but it doesn't matter now because there is no reversing course on aggro. Once mobs are pulled, they'll be attacking until either they die or you all die. Are you going to do your job and tank, or are you going to sit back and complain/feel wronged?

If you don't step up to your responsibilities as a tank or leader, you are failing at your job.
A lot of players who run on tank roles don't seem to understand this, instead acting as if they have special status and only need to do things if they feel like it. That is the "tank entitlement" that many people are talking about.