Why do people think it's odd to go shopping alone?

I am a 23 year old female at university. Like most women, I LOVE shopping. Whether it's for food or clothes. Just love it. Shopping with friends is fun but I rather shop alone. I enjoy going for days out with friends just to browse but sometimes I go into the city centre to look around by myself. I feel bersalah when I need to buy something and I have a friend with me because they have to wait with you while you choose something, you have to wait while they go to shops they like. Kan macam menyusahkan your friends tu kan? It's so much easier when you're on your own you can just go where and when you like. But I'm self conscious now because my friend saw me in town and asked who I was with. When I said on my own she started laughing and goes "you weirdo I would never go shopping on my own"! What do you guys think? Do you go shopping on your own or is it odd?