Because it's a feature that is less known or less appreciated on Mastodon:

Hide Boosts

Have a person you like to follow, but they boost a ton of stuff you don't like? Click their profile, go into their menu (like where you would block them) and there's a hide Boosts button.

It's legit made it possible for me to not unfollow people entirely when they boost too much irritating or triggering or whatever content.