My gf is a waitress and in school, and if someone tipped her in bitcoins i would be furious, she has no way to use that. Its bullshit you try and push what you use on other people, forcibly. It's no different than going to another country and forcing them to take your currency and not use the local currency. Its a bunch of crap. If you can pay for the meal in fiat, pay for the service in it. Don't leave someone hanging on bitcoin because you think you're clever, you are only fucking them over. People pay for their lives in fiat, her university sure is hell not going to take bitcoin, nor should she or anyone else without their chosing. They dont need some shit they cant use making it more complex. Use legal tender.
so you would be furius at bitcoin, yet acceptable that her employer can get away with only paying her $2.50!
tell her to get a different job.
as for bitcoin. when she was given the tip it was worth X, by the time she got home it was worth X+, and then by locating someone on localbitcoins to cash out the next day at a price preferable to her its worth X++
name me a fiat that can increase in price just by holding it on your phone for a few hours.
and as for FIAT tips if i gave someone $5 that waitress would not take home $5, she would end up having her manager request her to share it between the other staff and the manager. giving her maybe $1, maybe less depending on how many other employees there were.
so again if your GF is a waitress, dont argue that she received bitcoins as a tip. argue that she is in a dead-end job that does not offer fair value for the time she gives to that business.