The tradeoff is that if you use a property management company, most of the profit from your properties flows to them, because they don't work for free. There is also a non-negligible risk involved in moving your control of your assets over to a barely-interested third party.
Truly passive income is rare, and it always involves a dollar-and-cents tradeoff in how much profit and oversight you're willing to forfeit to others in exchange for open time.
Very few people are Scrooge McDucks with all the time in the world to swim around in a vault full of gold coins, and of those rare people who could, even fewer actually find that to be a worthwhile use of their time.
The key takeaway here is that everyone has got their problems and concerns, and in this competitive world, it is naive to assume that anyone can maintain their position without significant effort.