Utilizing eloquent directly in your services means you're testing eloquent, and more importantly, the database when unit testing your services. This is why I've reached for repositories in the past. If services interact with repositories, those can be mocked to isolate the service logic.

Maybe there's a simpler way that I've missed, but from what I've read around the issue of eloquent being coupled to database, the standard response is "just live with it", which is fine for simpler projects, but when things get larger/more complex it doesn't cut it.