It is clearly nothing like as simple as that, even in the least complex situations. Regardless, you are missing a key distinction.
There are three roles for people involved in a pregnancy, the biological father, the biological mother and the person who is pregnant. The biological mother and biological father have exactly the same sets of rights and responsibilities and a person who is pregnant has a different set of rights and responsibilities. In most cases, the biological mother and the pregnant person are the same individual, and so that individual has the combined rights and responsibilities of both roles. The biological father obviously only has the one set of rights and responsibilities.
With surrogacy though, the biological mother and the pregnant person can be two different people. In that situation, the biological mother has exactly the same rights an responsibilities as the biological father and the surrogate gets the rights and responsibilities of a pregnant person. That can include the right to abortion (in given situations depending on the relevant laws).
The distinction with the surrogacy example demonstrates why there are obvious differences between the situation of a mother and a father in a conventional pregnancy. There isn't a double standard because they're not in the same situation. They're both biological parents but only one of them is pregnant. If a man could ever get pregnant by some means in the future, he would have the relevant rights and responsibilities, including options for abortion.