It's definitely an issue if you're treating main as 'good to deploy'. Also with more devs the chance of this happening is pretty good. Definitely want to enforce a branch is up to date before allowing merge (though with a lot of devs this can become difficult) not sure if there is some sort of merge/test pipeline solution out there.

It completely depends on your organization's merge volume and your codebase's complexity. I've seen it happen many times working on a large monolith. But requiring a passing integration branch build before merging to master, or a merge queue, solves that.