I've never quite understood, do people collect so many amiibos just for the sake of making a big collection, or is it because they actually really like their in game effect? My only amiibos are Mario, Yoshi, DK, Link, Kirby, and Diddy Kong, and I don't plan on getting all, or close to all of them.
With anything, people are going to have some "collect 'em all" feeling about it, especially if it's in relation to something they like.
Personally though, I only want ones for characters I really like or would use. These being Rosalina, Shulk, Mr. Game & Watch, ROB, and maybe Waluigi and Shy Guy if they're made.