It depends upon the repairs. Oil changes and similar are generally discouraged due to the high probability that you will leave oil residue behind. Emergency repairs are looked upon as an unwelcome, but necessary, evil. Repairs at any big truck stop is likely going to be discouraged on the assumption that you are creating a pretty high liability for a business required to keep things safe and control ALL oil and fuel spill within EPA standards.
If you have to change a tire that can likely be done anywhere. If you are planning to overhaul your engine it likely cannot.