There are so many failures in microservices that just can't happen with a local binary. Inter-service communication over network is a big one with a failure rate orders of magnitude higher than running a binary on the same machine. Then you have to do deploys, monitoring, etc. across the whole platform.

You will basically need to employ solutions for problems only caused by your microservices arch. E.g. take reading the logs for a single request. In a monolith, just read the logs. For the many-service approach, you need to work out how you're going to correlate that request across them all.

Even the aforementioned network failures require a lot of design, and there's no standardization. Does the calling service retry? Does the callee have a durable queue and pick back up? What happens if a call/message gets 'too old'?

Also, from the other end, command line utils are typically made by entirely different people with entirely different philosophies/paradigms, so the encapsulation makes sense. That's not true when you're the one writing all the services, especially not at small-to-mid-size companies.

Plus, you already can do the single-concern thing in a monolith, just with modules/interfaces/etc.