Cryptography. Your receipt is presumably only valid for yourself. So if you got someone else's receipt, it wouldn't be valid for you.
I support paper voting for political elections for most of the reasons you mentioned, but I don't think that automatically makes all arguments for paper voting good and valid, and all arguments for alternative voting systems null and void.
And even if political elections are better done on paper, there's plenty of other elections (eg in companies and clubs etc) with different requirements and threats, and they might benefit from the research and experimentation.
Cryptography. Your receipt is presumably only valid for yourself. So if you got someone else's receipt, it wouldn't be valid for you.
I support paper voting for political elections for most of the reasons you mentioned, but I don't think that automatically makes all arguments for paper voting good and valid, and all arguments for alternative voting systems null and void.
And even if political elections are better done on paper, there's plenty of other elections (eg in companies and clubs etc) with different requirements and threats, and they might benefit from the research and experimentation.