It might do, you are often not allowed to wait around as you walk from the plane to the terminal building and to passport control. You may be in different places in the queue. Now say one of you goes through to the first place you can wait, perhaps after passport control and before baggage collection. The other person doesn't turn up. You don't know why? Wait another 10 minute? Did they go through baggage area? Passport issues? Where do you meet now? You can't help them. Granted mobile phones, but not being split up is easier.

Now friends sometimes end up in different seats, and you can probably get away with waiting somewhere, maybe on the plane itself to meet up, but if everyone is in the same boat it might be chaos to do that, and there is more incentive for airport staff to stop you.