because those will protect you if your not home. If you want a gun, get one. If you dont want one, dont get one. I do not have expertise in the home security field but I can recommend a good dog, I got a lab who barks when someone is at the door, she is a sweetheart but I think the bark is enough to deter someone from breaking in.
If I was going to have a home Security I would probably go with a DIY system and the first place I would go is here:
http://www.cnet.com/news/diy-home-security-roundup/