I was just having a similar conversation with my sister who manages assisted living facilities. I don’t know if it’s the same for in home caregivers but in facilities, it is illegal (in the states she operates in anyway) for the staff to accept gifts and gratuities because of the high potential for elder exploitation.
I don’t know if your caregiver is hired privately or through an agency, but if they are through an agency, they probably have a policy prohibiting tips.