Why do some stores charge for bags?

Excuse me, I've been noticing lately that some retail stores are now charging for bags, and it's left me quite curious. Could you perhaps shed some light on the reasoning behind this practice? Is it an attempt to reduce waste and promote sustainability, or is it simply a way for businesses to increase their profits? Additionally, do these charges vary from store to store, or is there a standard fee that's typically imposed? I'd really appreciate your insights on this matter.