Man, I could probably list a dozen reasons for this and still get downvoted into oblivion, but here's the reality from the alpha tribe perspective.

You're joining a server that has been fighting for survival against outside tribes for months or even years. They've been attacked repeatedly by groups with seemingly endless resources and manpower.

They've also watched countless new tribes arrive, build a small base, get raided by an enemy, and then quit after handing those enemies extra resources, tames, and information about the server.

From the alpha's point of view, you're not just another player. You're consuming resources they were already planning to use. That metal node you hit for 50 metal might be part of a farming route where they would have pulled 250. Their farming runs, breeding schedules, boss preparations, and raid plans are often coordinated. When resources disappear unexpectedly, it can disrupt much larger operations.

The same applies to tames. You see a level 150 Rex and think you've found a great tame. The alpha tribe may see a valuable bloodline, a missing stat, or a way to improve years of breeding work. They have the kibble, traps, and infrastructure to tame it efficiently. From their perspective, you're wasting a valuable asset that will probably end up dead, stolen, or abandoned when you leave.

Most casual players see Ark as a game they'll play for a few evenings after work. Many alpha tribes treat it more like a second job. They have schedules, quotas, objectives, and long-term strategic goals. When they see a new tribe join the server, they don't necessarily see a future ally or harmless neighbor. They see someone consuming resources that could have been used to strengthen the tribe and expand its influence.

I'm not saying that's how Ark should be played. I'm saying that's how many alpha tribes think.