First off, you find those suits. You can't use them, but hey its POWER ARMOUR. So from Fallout 3 you know that the BoS will be the most likely guys to teach you how to use PA. So what I do when I come across those suits. I take them to my safe house and stash it for when I can use it. If nothing else they are worth caps.
Also the Brotherhood teach you how to use PA. The Brotherhood give you a KEY to their safehouse. They sent you on a quest to find six suits of T-51b power armour.. So people are complaining because all you get is a busted up suit of T-45d?
There are way more quests to help the BoS than there is in Fallout 3. They give you a base, they give you training. You can replace their leader, you can blow them up or make peace with them. You can buy stuff from them. You can even try to change their ways. That is a lot of interaction with them.
Fallout 3, you don't even become a bos till the DLC. You don't do anything to become one, they just let you help them when it comes time to attack the Enclave. You get one BoS companion that is useless. The most they do for you is train you.. That's about it. How many quests do they ask you to do? I can't think of any. There is that one to save the guy but that isn't much of a quest, that is more like tagging along.
Some people haven't played FO3 js they don't all know, also you don't do anything? You get the Geck, they obviously hear of your endeavor somewhere down the line, to know that you're valuable asset to them, just like Enclave consider you that par colonel Autumn, then You have the purification code for the project, so they need you, more than you need them, just as the Enclave do.
So you kinda do earn your place in the BOS imho, but hey each to their own, and like I said from a role player perspective you'd not take the random armor you can't use, just like he says there is no immersion with the BOS in this game, I mean why must you compare it to FO3, this is a discussion, not a comparison to 'win' an argument after all.
Plus you only become part of Lyons Pride in the DLC, you are BOS in the final stretch of the game with Liberty Prime.