Many small dogs seriously dislike humans towering over them to pet them from above or, worse, to scoop them up. My son has an 8-pound miniature dachshund who has a bite history because people can't seem to resist doing that. They got her very young and there's no reason to think she's ever been abused. The first time I met her, I sat on the floor and just waited for her to come and introduce herself. We've been pals for years, but I still can't safely just reach over and pick her up without plenty of warning.