How should I properly drop off used clothes?

Feeling somewhat productive today, I cleaned out my closet and got rid of about 40-50 old shirts. I put them into a couple of laundry baskets (the clothes were clean albeit old) and took them to a local used clothing store that benefits a charity.

While they accepted my clothes, they warned me that the next time I needed to bring the clothes to them in garbage bags. They wouldn’t say way except that it was “easier to sort that way”.

Why would this be? All they did with my clothes was dump them on a table. And presumably someone will sort through them to see if anything can be sold. The rest will be tossed out.

If I brought them in a bag wouldn’t the process be the same except that they would have to take them out of the bag?

The non-profit organization I work for runs a thrift store. I have never worked there, but I have walked through the back area where they put the new donations when they arrive. Imagine a room a little smaller than a half of a basketball court. In this room there are piles and piles of assorted stuff, some up to 8 ft. high. Sports equipment, kitchen stuff, appliances, shoes, clothes, tools, toys, magazines, music, etc spread out all over the place with new stuff everyday. I know that they have a team of volunteer retirees that come in a few times a week to sort through the stuff/junk. This takes a great deal of time, and sometimes the stuff has to sit awhile before it can be sorted. I am guessing that by placing the clothes in plastic bags, it makes it easier to store and move around until they are able to sort them into keeper and not keepers and then sort the keepers into sizes and genders, then price them so that they can be put out on the floor. Another guess might have to do with the back storage room smelling horrible! It smells like rust and dust (kinda like a basement or a garage that is used primarly for storage). Perhaps the bags keep the clothes from getting dusty/smelly and/or keeps the clothes from making the place more smelly.