There is good reasons to break out projects into multiple crates. It makes reusing functionality elsewhere easier. It makes it easier to reason about behavior. It makes it easier for LLMs to understand (either working within the crate or consuming as an api surface.) So you end up with projects that have multiple crates inside the same workspace and it really blows up dependency count.

The other very important reason for splitting into crates is compile times. Crates are the "compilation unit" and you often get more build paralellism with more crates.