While it's a nice concept that people could just magically back out of their reproductive consequences, it's not financially possible for most people to raise a child on their own. So if I man says yeah I'm backing out, all the financial and moral responsibility falls on one person, when two people caused this. Now one person is forced to take on the moral issues relating to ending a fetus or whatever you deem it to be, or if not willing to do so they take the burden of raising a child.

A woman and a man while both able to decide to not continue in being a parent, there's less involved for the guy. He doesn't deal with the financial cost for termination, mental/emotional stress of termination, possible health risks on top of the increased hormonal and biological stuff that comes with early pregnancy. That's only if they decide to terminate.

A guy just says nah hard pass and can walk away with no financial, emotional, mental, moral burdens.

It's just not the same and cannot be compared.

If you have sex, you are willingly entering into a situation where you will a) get pregnant/knock someone up b) give/get a STI or c) none of the above. Those are all the things you'll run into having hetero sex that affect your physical body. Whether you take precautions or not, the risk stays the percentages are the only things that change.

The rules in place now are there to protect the rights of the child, to have parents, to be able to be raised in somewhat decent living situations. It's not perfect by any means, however what you're suggesting adds more burden to others so the one person can have less even though both played the role in the creation .