My biggest issue about tipping is the arbitrariness of it. Why do delivery people get tips (pizza, waiter, porter, taxi, etc), yet other low income workers don't? If you worked low income jobs without tips, the entitlement of the tipping workers is off putting. Also this is an international audience that may have tips, but not the different minimum wages for tipped workers that is unique to the USA. Within the world of low income workers, there becomes a split of the untipped and tipped, and the tipped are basically the higher paid ones, which feels hypocritical when they complain about it while your sitting there without it.
Then you get into the naked racism, ageism and sexism that tipping exposes in who gets tips and what the tipping professions think of those various groups too.
Move on to later in life when you have better jobs, and the entitlement of the tipping classes and tipping alumni makes you eye roll inside because you never had that favor.