I've been living abroad for over half my life in a country where tipping is not the norm. At most you would round up. 19€ bill? Here's a 20, keep this change.
Going to the US soon to visit family and the whole idea of tipping makes me nervous. It seems there's a lot of discussion about getting rid of tipping, but I don't know how much has changed in this regard.
The system seems ridiculously unfair, and that extra expense in a country where everything is already so expensive really makes a difference.
So will AITA if I don't tip? Is it really my personal responsibility to make sure my server is paid enough?
To sum up, if you work in a business that relies on tips, you will defend the crap out of tipping and will be biased towards tipping uncontrollably.
If you are a business that wants to squeeze every penny, you will encourage and propaganda tipping as much as you can.
If you are anyone else you will wish for something different.
I recommend that you tip when the app says to tip, just simplify your life and if a screen says add a tip choose the minimum for now and don't worry about it yet.
Tipping used to be a way to implement a truly granular free market (or however you want to justify it, that's besides the point). Point being is, it's how service workers largely get paid. So regardless of how we got here, to not tip them is to not pay them fairly for their work. The problem now is that commerces turn tipping on by default at point of sale devices indiscriminately. So tipping when you see the screen is poor advise as it just gives into greed and manipulation. Follow the original rule: you tip when there is personalised service rendered, for example restaurant waiter, or driver, or barber or hair dresser. If it is neither personalised, nor a service rendered by an individual, you never tip.