These Apple people are not demanding all customer's tip them... nor for Apple Inc. to tip them. I suspect that in service to some customers, some of those customers offer them a tip in appreciation. Apparently, they can't accept any such tip right now. They are apparently wanting that policy to change. If a customer offers them a tip, they want to be able to take it.
This is not about seeking a tip for a simple transactional service like selling a phone. But maybe someone spends 30 minutes to teach someone how to solve some problem or how to use some app features, etc. And that 1+ person objectively wants to give them something for good service. I'm not sure "we" should be passionately against it. That's between customer seeking help and the person delivering the help they want/need. Some customers might want to tip. That's THEIR business.
Someone comes in with all of their (subjectively priceless) data apparently lost. An Apple representative is able to figure out that its not really lost and helps them recover it. It's not hard to see that panicked customer perhaps wanting to reward the help with more than just a "thank you."
No one would ever be forced to tip- just as it is in all transactions. But if some customers want to tip for good service, that's not exactly an unheard of, insane or greedy concept. Those in industries where tipping is "normal" would even argue that the potential of getting some tips motivates employees to try even harder to deliver outstanding service... to EVERYONE (because even those purely motivated by tips doesn't know until AFTER they deliver service whether they get a tip or not).
If it's not mandatory to tip, I don't personally see anything wrong with this want at all. When my hot pizza is delivered on time in a little while by someone with only the skill of driving, I'll likely give them a few dollars. If my car won't start and someone pulls over to give me a jump to get me rolling again, I'm very likely inclined to give them something for their time & trouble too. If someone spends some service time at an Apple store teaching me how to do something I can't figure out, it's not like I would naturally NOT be moved to tip for good service either. Is pizza delivery or broken down car help and in-person tech help/services so different that only the former should be OPTIONALLY tip-able? I don't feel that way.