Question about Ritual Purity and Family Purity

I understand that there are specific prohibitions in the Torah about having sex with a woman who is ritually impure.

• Men are prohibited from having sexual relations with a woman who is niddah

However, I also understand there are the family purity rules, like where during menstration you have separate beds. I suppose my question is the following:

Q: Is the rabbinical fence because of the definition of “sexual relations” ?

Q: Or is this because the individuals don’t want to become ritually impure. If so, why does ritual purity matter if there is no temple? Just pre temple prep?

Thanks and I appreciate yalls community!