About the Hyuga marriage outside the clan.
It is a normal conclusion since they don't want to unveil the secrets of the Byakugan because that's why Hinata was captured when she was younger. For her ocular powers.
Marrying outside the clan would mean that those secrets will be unveiled.
But she was kidnapped because the Cloud nin wanted to cut her body apart.
I'm sure there are many good reasons why clans would not allow marriages outside of their clans, but until we actually get told by the manga, I personally think everything else is just speculation.















