I'd prefer to keep a receipt for myself, with a randomly generated serial number on it, so at some point I could verify that the digital record of my vote #158FA134 matches the paper receipt and who I voted for.
Jim is not a nice man and is very demanding and abusive and goes to vote. He wants his wife to vote for X, but he suspects that she will vote for Y. Today, she can vote for X or Y and tell her husband that she voted for Y. He has no way to prove her wrong. With receipts, he can tell her, on no uncertain terms, that she is to show him her receipt afterwards. If she doesn't produce a receipt showing she votes for X, he'll beat her. With receipts she does not have a free vote, without receipts she has a free vote.
I want to buy your vote, and will pay you €10 to vote for X. Today, you can vote for who ever you want, and tell me you voted for X and demand payment. I have no way to prove you wrong. Hence vote buying is hard to do, because you can't know if you're actually buying votes. With receipts, I can ask to see your receipt, and only pay out if you vote for X. With receipts, vote buying now becomes an actual thing that I can do.
Employers could now request that employees tell/prove/check who they voted for.
Unions could now tell/prove/check who their members voted for.
Churchs could now tell/prove/check who their members voted for.
It's one of the biggest challenges in crypto-voting systems. And there are some solutions. But we need to hammer down on the "silly people, why not just print a receipt" idea really hard.