> If you have to hold USD to buy and sell USD products (as a European)

Do people do this? Up until some months ago, I was heavily invested in some US companies, and I never actually held USD in my accounts at any point. I used EUR to buy those stocks, the conversion happening together with the purchase, and same thing when I sold them, I received EUR ultimately.

I know I could have another account in my bank with USD set to the currency, I just don't know why'd anyone would want to, when you can convert at the point of sale/purchase. Of course, if you're doing forex trading or whatever, that might make sense, but I don't think generally people hold USD to buy/sell US stocks, because you don't have to.