Do I have to tip the bartenders and hotel staff, when a U.S. University hosts an event for researchers? Prior to the COVID-19 lockdown, I attended a generously-funded research meeting that included a hotel stay, free dinners and bar drinks.  There was a dedicated bar section just for us.  

I always wondered: At these funded events, should I tip the bartenders and hotel staff, or can I assume that the University takes care of not only the bill but also the gratuity that is expected by the service staff? 

I landed up tipping on most times, but the few times that I did not, it felt a bit awkward -- walking away with a beer without tipping the bartender seemed rude
It is typical for catering contracts to include some sort of 'service fee' that serves like a 'tip', and you can assume that the staff are paid a better base wage than tip-supported employees typically are. Even regular restaurants often have a non-optional 'tip' added on for larger parties (thresholds vary but "8 or more" seems common).

That said, employees in these businesses are not high-income earners, and probably make less total take-home pay per hour than their tipped equivalents (bartending, especially, can be a relatively lucrative position in the service industry at the right venue).

If you appreciate their service, if they do something above and beyond, if you're in a generous mood, or if the cost makes you feel less awkward, feel free to tip; it won't seem like you are throwing money around or anything negative like that.

If you don't have cash and especially if you aren't asking for anything special, you can have a clean conscience that you haven't committed a faux pas by not tipping in this circumstance.