This custom may seem absurd to you, but it has proved itself over successive generations. For example, like you, I am a Sinclair because my Father and is and his patrilineal ancestors were also Sinclairs. My Mother is/was a Fraser but as is the custom and practice, she relinquished her name on marriage. I think my Father would have considered it absurd if his children were Frasers!
I have to assure you that my paragenetic links to the Frasers do not dilute my Sinclair-ness, even if you assert that the matrilineal genes are stronger!!
Euan 'Heldonside' ;-)