No. That could be the way it goes, but it's not a requirement (unless it was some religious rule or something, I guess).
In any relationship, there will always be somebody with more power over somebody else (Boss v. Employee, Student v. Teacher) with the exception being a love relationship, since there's an expectation that both partners care about each other equally. However, when there's multiple partners, somebody is going to become the centre of attention depending on who has the most partners, and there may also be favouritism involved.
This is ridiculous...
How so? If somebody is entering a polygamous relationship and keeps finding new partners, how long does it take before you are spending barely any time with each individual?
A: First of all, being married doesn't mean you have to have kids.
No, but there is both an expectation on a natural/biological and a social level that you will have kids with a partner. The reason love feels good and that the body is designed the way it is, is that so we can continue to produce more offspring.
Second, if you do have kids, it wouldn't hurt anything for them to be raised by only one of their parents half the time.
You've clearly never lived in that kind of family structure, or in a structure where one of the parents is totally missing. I know a lot of people where one parent was practically never at home (similar to my Dad) and they're usually pretty pissed off about it. It's no a good environment to grow up in.
Third, why are you even assuming that spending time with one partner means being away from the other(s)?
There's only so much time in a day, and somebody has to earn money to support the family. Furthermore, if you're in a polygamous relationship with kids, it's likely there's kids with the other partners and so you'd have to split time evenly. Kids are not very good with the concept of "sharing" and when they're young are far more dependant.
B: A meaningless symbol. Just because you want that doesn't mean it's an objective (or "logical") advantage.
The whole point of marriage is to form a pact with the one person on the planet you truly love more than anybody else. There's no pointing having marriage if you're going to just sleep with anybody you please.
C: Also ridiculous. If we all became gay, the world would end. That doesn't mean there's something wrong with homoloveuality.
But it does mean that we need to have a substantial more people who are heteroloveual to allow for continued birth.
Furthermore, THEY'RE DIFFERENT ISSUES. Polygamy means there's a smaller gene pool, and thus a risk of more genetic defects. It doesn't mean people have to stop reproducing.
