Part jealousy, part disagreeing with the system. When I first heard years back you could get paid for doing this I was like no way but it became a reality and a lot of people are unhappy about this mainly due to the fact of how it works.
Someone who has an office job to get up and 7AM to get a train at 7:30AM to be at work for 8:30AM then come home at 6PM and just about get enough money to eat for the week and pay his/her electricity bills just to make a living and sustain his/herself. Then they turn around and see people like us who can get up whenever we want, open a computer, play games, talk into a camera, go to bed and make more money than the office job could make in 2 weeks with overtime. I mean I can easily see why that would annoy someone it even annoys me. Then they announce shirt selling, sponsorship deals, how their going on vacation bought a new car while I'm here eat the other half of my canned soup with 2 slices of bread about to go to bed to get up at 7. I mean just thinking about it annoys me right now but thats how it works.
I don't hate people or larger YouTubers who make money, as long as they don't flaunt it, constantly mention it or show off at the fact they have all this money. That's what annoys me