So your approach to preventing fraud is... to trust people not to defraud you?
Glad it worked for you with bitcoin and the particular people using your service, but that's not really a good basis for a payment network. There are multiple other problems with bitcoin as a payment network and currency, the delay in transactions (which prompted your experiment in ignoring a key part of the currency) is only one of them.
If you run Starbucks and serve 1000 transactions per day, you’ll have some fraud. If 0.1% are fraud, that’s not too bad.
1-The current solution is worse on this dimension.
2-Since Bitcoin Cash doesn't have replace-by-fee this is impractical for any small transaction.
3-Most of the situations that need to be immediate are small--with the large ones it makes sense to wait.
Actually, it really is. I've been accepting 0-conf transactions for nearly a year and had negligible double spends. https://incoherency.co.uk/blog/stories/zeroconf-payments.htm...
The small number of double-spends that did occur since I wrote that blog post I think are mostly due to bad luck (and opportunism) rather than malicious intent upfront, and represent only ~0.1% of payments.