I agree and that was mostly our thinking when we decided to not put out a demo at the start (and also the quite cheap asking price) I suppose the benefits of a demo would be…
Not everyone knows about steams refund policy
The gameplay can make it look quite a frustrating game (which it can be at times, but we have really tried to work around this) so a demo might encourage people to try it out and hopefully show them its tough but fair. (And even generous in places)
Not sure this all adds up to a strong argument either way but just thinking it over.
I think the biggest problem has always been visibility in general, we are terrible at promotion and left it very very late.