Why not let foreigners vote? Why not give them free healthcare? Why not subsidize their education abroad? Why not let foreigners pay our politicians to make

Why not let foreigners vote? Why not give them free healthcare? Why not subsidize their education abroad? Why not let foreigners pay our politicians to make legislation - the money goes to lawyers, consultants etc. i.e. right into the economy! For the same reason we have borders, that we don't allow foreigners to buy some kinds of assets (i.e. wireless spectrum) - or do some kind of banking, own certain kinds of companies.