It’s not my company's business as to who I am allowed to date or engage in a consensual relationship with. It literally has nothing to do with them.
For example:
If you date someone who works for you, and you have multiple subordinates (as most managers do), and you rate / evaluate those subordinates (as most managers do), and you rate your partner higher than another subordinate, you are opening the company up to legal action that you discriminated against the other subordinate due to your relationship. That costs the company money to defend and more more if they lose, so they have every "business" to tell you not to.
There are many more examples.
If I could have my way, we'd ask ourselves why do managers have so much sway and power over our lives in the first place, that their bad moods and habits can literally kill us? If people cannot be trusted to be managers when normal human emotions and interactions occur, then why are they managers in the first place and why do they have so much power over us?
Also, hypergamy doesn't require that the two parties work at the same company, so it doesn't seem relevant to this discussion.