Look at the bags into which you place customer purchases. What do they say about your business/ What do you put in the bags to entice customers back?
If your bags are generic, not of the brand of your business then you are not marketing your brand effectively. If the bags only have the purchases then you are missing an opportunity to entice shoppers.
If you are concerned about declining traffic and or revenue, managing bags as a marketing activity could help you improve your situation.