I have reached the same conclusion even without any Bonvoy credit card.

The problem is that it makes sense to buy a huge amount of it, but then the bigger the amount, the more $ you would lose if someone did steal your card. Also, the interest rate is pretty high at the moment, I know you won't get 20% return on your investment, you get something like 4+% here in Scandinavia if you put them into a bank.

Another minus for non-USD earner is that USD is too high at the moment, so it makes zero sense to buy the card and use it next year (it's very likely that USD will drop a bit next year). Furthermore, the US has gotten so expensive that I found out that even if the airfare is $300 cheaper per person to fly to the US, it is still cheaper overall to visit Japan from Denmark (as long as you are ok with staying in Japanese business hotels). Not to mention the insane increase from $12 to $21 to get a ESTA just to enter the US vs. 5 EUR for the EU and the ESTA only lasts for 2 years.