Why do relationships NERF people so bad?

In case you don't know what NERF is; it's an internet term (formerly a gaming term) when the power of a weapon or character is reduced drastically in an update. It has been co-opted to describe real life situations as well. So to describe the situation, I have a friend who moved in with his wife. He is a graphic designer and he was a super interesting and chill guy (he still but not to the extent that he used to be). He used to hang his own made posters on his walls, had an entire hotwheels collection on his bookshelf, he used to collect various indie comic books and display them etc. Recently he moved to a 'better place', a pre furnished apartment with no space for his work station, his wife has hung up some generic Tim Johnson looking paintings in their rooms, his bookshelf is nowhere to be found. I asked him what he thought of the house, he just shrugged. I asked him where his stuff went, he shrugged again. And this was me meeting him after a month, our hangout frequency has been reduced from weekly to monthly, mostly because he's too busy entertaining guests, his parents, her parents, her friends etc. The thing is that this isn't the only person I've seen this happen to. I can recall at least 20 people who I just stopped hanging out with because they just became boring husks of their former selves. Why? how do you let this happen to yourselves and be okay with it? Is the reward of having some company worth the price of letting yourself be consumed by your partner? Shit like this makes me so afraid of committing.