Yesterday an article on tipping hit HN and this reminds me of it. When you remove barriers people spend freely. Start throwing stupid pause moments, the value doesn't match the advertised price because of x fee, y tax, z undisclosed service or an outright wall screen begging for a tip, and people slow down their purchasing. It will be interesting to see an impact here if this goes through and it could be instructive to the value prop that tips bring to industry. You may think you are externalizing a cost but maybe you are really harming sales.