Comment by Swizec
What does team size have to do with this? Small teams can (and should) absolutely build modularized software ...
You simply cannot build a [working/maintainable] large piece of software if everything is connected to everything and any one change may cause issues in conceptually unrelated pieces of code. As soon as your codebase is bigger than what you can fully memorize, you need modules, separation of concerns, etc.
Sure I agree with that, but microservices are just one of many ways to modularize software/achieve separation of concerns.
I assumed you were talking about team size specifically because that is the thing that a microservice architecture uniquely enables in my experience.