Single family gets more tricky because the value is more closely tied to the property value and not the rental income. I think this is where the inventives are often misaligned. Even so, the best property managers will handle a lot more than just filling units, collecting rent, and handling maintenance. They understand the goals of the owner and will adjust their management strategy to meet those goals (eg income property or a quick sale in a few years).
To add to your list: tenant retention (highest cost is actually unit turnover), setting rent to the right amount based on local comparables, and keeping in compliance with the ever changing rental laws.