oh i see what ur talking about. i feel the same way about friends getting into relationships. i had a friend who got a gf and completely ghosted me and my other friend (we're both girls) and only came back to talk to us after him and his gf broke up

i also wish i understood why friendships suddenly become undervalued when romantic love is present.
i don't have much advice because i've kind of accepted that the bonds i have with people are susceptible to change, as are most things in life. i shy away from people because of the inevitable (or lack of anything lol). all i can say is letting people take u for granted is preventing u from enjoying how ur friendship is now because ur worried about how it could be in the future. if this is the outcome of being overly available to people in hopes of them doing the same for u then it's not worth it.