Why Santa Claus is supposed to bring gifts only for kids ? Why not for everyone ?

It kind of depends on your families traditions. When I was a little kid, a gift from Santa for me would always show up on the table as well as one for my mom and my dad. My parents kind of just like surprising each other with one extra little gift every Christmas. My family and my fiancee's family all still exchange gifts from "Santa" every year, even though there are no young children anymore. It's just kind of fun. No one says Santa has to be for only little kids, if you want to leave a small gift for your husband or mom or whomever from Santa, that's fine :-)