It completely depends on the industry and the worker's rights if you ask me. Where I live, tipping is pretty unusual and unnecessary because the industry functions as normally: prices are based on some measure of cost+profit, and cost includes the full remuneration fee for the worker. Tipping as a way to supplement a deficient salary is a ridiculous business practice that doesn't exist in most industries. I don't tip the bus driver, my teacher, a retail store worker, a police officer or bank manager that provide products or services to me, either.
Now paying a small extra on the basis of quality of service, does make sense. But again, that's different from supplementing a worker's deficient salary. The former is merit based, the latter is, on average, a necessary, expected and you could almost say culturally mandatory pity/solidarity payment by the customer that ought to simply be priced in the product or service and arranged between employer and employee.
Paying extra based on merit does make sense in some industries, like say a tour guide who didn't just tell you the facts of whatever artefact you walked by, but made sure you had an amazing time, catching your interests and focusing on things that resonate with you, waving stories into a unique experience, that's tip-worthy. A restaurant worker who puts in extra effort might be, too. But a delivery man who mostly has 1 actually important parameter of quality 'being on time or not', mostly, that's not a tip-worthy parameter in my opinion, that's just his normal job, and if he's getting a decent salary, I wouldn't tip for that.
I'll happily tip anyone doing his job if it's necessary to supplement a deficient salary, but I wouldn't tip anyone just for doing their job if their salary is sufficient. Whether that's the case for this particular uberised delivery industry will play out soon enough. I'm over in the Netherlands, generally tipping is not done and not necessary either as salary levels are quite decent. (the only exception is youth-wages, which are beyond ridiculous and a movement is on the rise to do away with the concept).
