That's the general perception from men and it's a dumb one.
It boils down to the same thing most of the time Concerns over children.
In your scenario of making near the same money, you're neflexrinf to consider a few things. Allow me to enlighten you.
1. The woman may or may not have an easy recovery period from childbirth. If there was any kind of drama during delivery, which happens a lot more than you men seem to be aware of, there's going to be a sizeable hospital bill, even with insurance. I had some mild drama and we were both fine, but I had a long delivery and was kept for monitoring because of that drama for two extra days. Total time in hospital to have my daughter: 6 days. Do you think that was cheap?
It took me 10 years to pay that off.
You don't want to think too hard about how financially devastating having a child who ends up in NICU is. It'll curl your hair for you.
I was the picture of health. Once I got past the morning sickness phase, my pregnancy was smooth sailing. No expected complications. And there were still problems. The point here is that you can't tell if you're going to have problems delivering or not.
The only thing you can do is prepare for that eventuality as best you can.
That means making sure, in one way or another, that if you're stuck with a big hospital bill or forced out of work for a while that your partner can cover that deficit.
2. The more children you have, the more one or both of you are going to have to scale back work to care for these kids. Also, the risk of ending up with one of those hospital bills goes up for every pregnancy and child you have. Let's not mince words, men on average always want all these kids but they don't want to be the ones to sacrifice their jobs for it. You men want us women to do that.
I've heard very few women say they want a large family but a whole lot of men saying they want to be able to field a little league team. With little to no idea about what it costs to provide for all those kids.
Show up with that paycheck then. Otherwise, you men can sit down and shut up until you're willing to be the one to sacrifice a career for a large number of children.
3. Child care. A woman will lose our on promotions and pay raises by having children. We call it the motherhood penalty. You are perceived as being less serious and dedicated to your career because you have children to care for. Big part of this is because it's nearly ALWAYS the mom who has to handle sick kids.
4. Another side of the above is that childcare, as in daycare, is incredibly expensive. A couple could easily lose 75% of so of one of those paychecks just on childcare, especially with multiple children. Average weekly daycare cost is $284 dollars in the US. A lot of women give up their careers because they simply can't afford day care. So again, it being with you is going to cost her her livlihood, show up with that paycheck, jointly find another solution and stick to it, learn to settle with not getting everything you want (in this case children) or sit down and shut up.
In conclusion, just because some of you men get to tra-la-ls through life without ever concerning yourselves with the realities of life doesn't mean that someone else is dissing you because they have to. You men REALLY need to get your heads out of your asses and check your priviledge on this one.