I don't know if it is only because the names Kermit and Grover are famous muppets that no one would use them. I have a friend who goes by the name Mickey, and even though he does get many mouse jokes I don't think it is unusual. I also know an Oscar. So the existance of Kermit and Grover might have some influence over parents naming their kids, but that cannot be the only factor.
Welcome to the Muppet Central Forum!
Sesame Street moving to Netflix
Jim Henson Idea Man
Back to the Rock Season 2
Bear arrives on Disney+
Sam and Friends Book