it will increase your library count, then you can receive collector badges and xp according to the number of games you have
Steam provides badges for the number of games you have in your account. The more games, the higher the level of the insignia and consequently the greater will be the XP of the insignia. This Guide cam
steamcommunity.com
edit: Idk if it's worth it for the xp, at least for me, because from what I learned by increasing my steam profile level it only gives more friends slots and space on profile. So would filling up my library with games i wouldn't ever play doesn't make sense for me. I think it would be way better if they also give us steam points :/