Here's a question. Would you feel the need to have a “side hustle”, if you were earning enough money from your current work?
I understand that there are people who likes to work, and I don't want to judge or to criticize them. However, if we had more than enough money, I don't think there would be too many people who would even choose to work, let alone to have a “side hustle”.
“Side hustle” seems to be another way of saying “you're too broke to have a free time.”