For the same reason monoliths tend to split when the organization grows, it is often more manageable to have a small number of services per team (ideally 1, or less).
It's ok if a service owns more than one type of entity.
It's less good if a service owns more than one part of your businesses' domain, however
People seem to forget that there’s a continuum between monolith and microservices, it’s not one or the other.
Multiple monoliths, “medium”-services, monolith plus microservices, and so on are perfectly workable options that can help transition to microservices (if you ever need to get there at all).
Definitely don't just stuff unrelated stuff into a service since a team that normally deals with that service is now working on unrelated stuff. If the unrelated stuff takes off, you now have two teams untangling your monolithic service.
That said, I'm a big fan of medium sized services, the kind of thing that might handle 10 or 20 different entities.