Distance, and route play a part and how much stuff I need to carry. Going for a major Christmas shop session is a pain on the bike because I start having to carry the weight and bulk of a pannier with me (which isn't even empty for putting things in, where as going to the supermarket I can put it in the trolley.
If I want to look nice and dress in a skirt/dress then many of those aren't suitable for cycling in, certainly not any distance but I do have some nice outfits I can cycle in.