Do you have a luggage tag on your bag? Good.
Do you have a tag or business card or some other form of address on the inside of your bag? I hope so.
The outside one can get torn or ripped off your bag. Yes, even the sturdy looking tags can get caught on something and ripped right off.
If you need to identify your bag or if your bag gets lost…having your contact information on the inside will be a big help in getting your bag back.