"She doesn't have one, so acquiring one would be about what she could do with him that she couldn't otherwise; he looks terrifying but she doesn't live in a place where that gives her any advantage in, say, a fight - which is particularly relevant to Juliet - because there aren't any other daemons for him to engage with and anyone else she meets at home won't know that they mustn't touch him, or if they found out they'd have an entirely incorrect reaction to the information. She has no strong incentive to separate, so she doesn't expect to be able to send him on errands without inconvenience and unpleasantness she could more easily skip. The only thing she could do with a daemon that she can't without is send him to snuggle up to her Sherlock. I think she's waiting to see if Steph will touch her."