p.s. I should add the caveat that Starbucks baristas in Japan do not ask for names. It's culturally inappropriate there so Starbucks doesn't implement their names policy in Japan.
Anecdotal evidence to the contrary: I'm in the UK and have known a few people from parts of Africa over the years, they've all had made up simple short names because they tired of people but being able to deal with their real names (either not being able to pronounce it, or making a big thing if it sounding strange). And it wasn't just a short nick-name based on their name that they use generally: their friends from the region would call them something different. Likewise a polish fellow in one of my current circles does the same (though I don't know any of his wider social network so don't know if this simpler name is used more generally).
It may be a regional thing (partly because some languages use sounds like "clicks" that we don't, so have difficulty replicating): I've encountered numerous people from the middle & far East and they haven't done this.
It’s hard for me to imagine an Aloysius adopting a Chinese name while visiting China for a few days say. Would he use a derived nickname like Loy? I wonder.
If you're spending proper time somewhere it makes sense to make it easier for people to communicate with you. If you don't they'll just use a name they can say to refer to you anyway.
I understand why Starbucks does it. It's part of their corporate culture and marketing. I've no strong aversion to it -- as I said I'm used to it now and it is what it is. But I just wanted to highlight some of the downsides for people with unusual names, even though as you say it's no big deal to find a workaround.
And there exist more universal systems that aren't dependent on a barista's ability to spell or pronounce an arbitrary name, and that doesn't require the customer to reveal or invent a name.
p.s. English names are not exempt from this. Imagine going to a non-English-speaking country and having a name like Cecil or Xavier (which Americans pronounce Ex-zavier).