It is a cultural thing (not a Christian thing).
Britan developed the custom of taking the husband's last name and omitting the madien name in the 14th century.
But this is not the custom of most of the world, including many Americans.
It is not the custom of most Christians.
So why would a Christian pastor refuse to marry a Christian couple who does not hold that English tradition?
Such a refusal is placing unwarranted value on one specific secular tradition.
Refusing to marry a Christian couple for holding Italian, Spanish, French, Hispanic, Greek, etc. traditions rather than submitting to British tradition is not (IMHO) correct for a pastor.
Weddings are typically a traditional event. It is about the groom, bride and God. A pastor has no right to place his own secular traditions in the mix.