USAA’s membership is generally limited to current and retired military personnel and their families, but over time I believe they’ve been forced to expand that by law. For example, under Federal law I don’t think a company can restrict its FDIC-insured banking services (and maybe its investment services) to a limited membership.
I was never in the military, but I have a mutual fund account. They will not let me have any other kind of account since I am not military.
Also, I can only have one kind of mutual fund account and cannot pick, like those that are military or ex-military.