I met someone that did this for career purposes. The only difference was that they both were gay. He had his male friends, and she had her female friends, both carried on their relationships very discretely and made appearances as a couple when situations demanded it. Both were very well off financially.
Marriage to me is a contract. I don't really believe in it, but I guess it serves a purpose for some.
As for sanctity, I think it's all up to what a person feels is sacred to them, for some it's, love, religion, a good life, or money. It's their lives, let them choose.