You want the reasons, well here they are:
1. I don't have a scale
2. I don't have time to research and respond to 150 different ship to locations to determine costs
3. The further away it is the more likely things will either get lost or damaged. Since the stuff is so cheap there won't be insurance on it so I take the hit.
4. I'm not a business
5. I'm selling this stuff really cheap as a favour to our membership, so any potential buyers can just do a little leg work themselves in return
Simple enough for you?