@kayden @Pixificial there are a couple things going on.
Favourites are kind of a bookmarking feature as well as a way to show approval. My list of favourite toots is useless if I just use it to mean "okay, I saw your message" the way it's used on other platforms. So in the case where I do that, I usually remove those trivial ones some days later. You can ask, "Who favourited this toot?" but not, "What toots has this user favourited?" except regarding yourself. Boosts don't have this limitation. The dedicated bookmark feature is a much more recent addition and hasn't had as much time to influence how people use the platform.
Many interfaces don't show favourites unless you click for details on the post, or if they do, it just shows "1+" instead of an accurate count. The stated reasoning for this is to make it easier for people who struggle with addiction to online validation. Boosts, on the other hand, are always sent to your followers (although they have the option to hide them) and appear on the profile page, so they're a lot more visible. If you regularly boost interesting content, it's almost as valuable as authoring it yourself in terms of how desirable your feed becomes, so it gains you more followers.