You're right, as far as it goes. Having a paper receipt is pointless, other than if you're selling your vote. Having an auditable paper trail in the hands of election takers is, however, an excellent safeguard. Hand counting random batches of ballots after they go thru the scanners is, or should be, standard practice. Electronic voting machines are bullshit because paper actually works better, particularly when voters can just mail in their ballots. It's hugely successful here in CO & everywhere it's been implemented.