This article discusses various aspects of tipping, but mostly now that we should be carrying around a wad of $5 bills to give out to doormen, valet parkers, bellhops. That probably doesn't sound crazy in NYC anymore, but it still feels crazy out here in the midwest.
Link: https://www.marketwatch.com/story/how-much-should-you-tip-housekeeping-when-youre-away-from-home-2019-02-19?mod=mw_latestnews