I assumed that if anything it was to prevent people being pressured in to voting a particular way (eg an abusive spouse) - what' wrong with selling your vote, surely that's still democratic: you've chosen to accept a particular candidate based on the outcome for you.
There is no reason to prevent someone from verifying that their vote was counted -- not vote buying (or the presumed ease thereof), not vote tampering or stuffing (really?), not potential outside coercion of any kind. Laws exist for all of these things already, and would not suddenly become unenforceable or ineffective in the presence of vote verification.
Coercive voting has disappeared because it is impossible for the coercee to prove to the coercer that they complied.
My granny used to tell of tying red ribbons (red being for the left) on the goats in the country and her mother getting a lift to the polls from the Tories (when women first got the vote) and voting Labour.
Verifying your vote cannot relate to ballot stuffing at all - so you can prove to yourself that you voted X, but I have 1,000,000 made-up votes for Y.
Besides just being distasteful, just handing over powerful positions in our society to the highest bidder seems like a formula for brazen abuse.
There is no valid reason, moral or technical, for preventing voters from verifying their votes were accurately counted, and verification does not enable any new crimes – but it does prevent the current crime where someone's vote is either miscounted or not counted at all.
Personally, I would like to have a receipt because I think the danger of my vote not having been recorded is greater than the danger of someone demanding my vote receipt off me.
Sure they do: use a lie detector and ask them.
Honestly, the situation you describe is the problem, not the presence or absence of verifiable voting. If you've got the mafia threatening your family, voting is the least of your problems.