Making someone a member is different from letting them visit. My current church has "open communion" so anyone professing to be a Christian is allowed to partake. I'd be really unhappy if an openly gay person took part. For all I know, though, that may happen now.
And, from an earlier post the membership has to do with things like speaking into the Church's decision making, correct?
I think this is one of the problems with the institutional model of the Church that somehow took over the relational model of the New Testament. I'm not enough of an historian to know when the change occurred but I am daily confronted with the issues a congregation faces when it owns property, pays staff, funds programs, and all the other activities involved in institutional Christianity.
I don't mean to deny the value of structure to a fellowship, just identify the difficulties when that fellowship becomes an institution.