I was told that I shouldn't run my rspec specs in a rails\_env other than test. 

What are the potential problems running specs in production or development? I run specs in both. I usually run the specs in dev unless I'm testing something that uses the asset pipeline. I switch to production for that and spend 15 minutes pre-compiling assets. Are there any advantages to using the test environment over my current methods?

I searched for an answer but nothing explained why I shouldn't use dev or prod.