What is the stuff at the intrances about?
I get the impression they are zealous at preventing theft. Fair enough.
Do they actually force you to leave bags ... they seem to search bags at the entrance and keep some.
Many people who come to mustafa are in fact staff of rich Indians who have the task to shop at mustafa and bring the goods back to India. They come straight from the airport with empty luggage in tow. Main reason for the counters is to stow those luggages.
If you notice, you can also only pay for luggage near the exists.