Abortion/Gay Marriage - legislation or constitutional protection

I always find the American over reliance on Supreme Court to enact protections such as abortion access or gay marriage to be kind of weird. As far as I'm aware, no other western democracy enacts protections in this manner and all are done through legislation.

Can I ask the members of the subreddit that believe "abortion/gay marriage is a fundamental right", who determines those rights, if it is NOT just a majority view of current society?

FYI, I support both, just curious on the concept of fundamental right vs majority rule.