TLDR: other subjects make prescriptions that people are more agreeable on because the relevant values (such as health for medicine, material utility for science, etc) are more shared and less conflicting from one person to another. Those subjects with enough shared common values are considered objective while morality is not, because the values underlying the prescriptions are not universally shared.
However, values that underpin moral commandments, make many disagreements among people. The underlying values are not shared. This is the prime reason why morality is considered ”subjective” and the rest considered ”objective”. The values underpinning objective things are accepted enough to be pervasive. Imagine:
”why value truth, your science has only brought destabilization to our religious society, what makes you think your science is better than our religion? (you can’t appeal to truth because I don’t care about it as much as the issues I focus on such as not having the destabilization of the social order)”
and so on. Science and math became objective because enough people shared the same underlying values.
I think the most popular problem people have with morality is saying it is subjective because people can choose not to follow it, or they are not forced to. However this is true of other things that are
Math and Science have a prescriptive component. Not everyone follows the scientific method.
Science has the scientific method, and math has its own dispute resolution prescriptions (how to resolve mathematical disagreements).
Yet even if you choose not to follow math science or morality, doesn’t mean that they are subjective. I understand subjective as dependent on the subject. So obviously what goes on in my brain may be subjective to me, but it’s objective to others so long as it does not depend on them.
Prescriptions on behavior, how to go about healing yourself (medicine), eating (diet), how to predict quantifiable information (math), how to predict reality (science).
So what’s the matter? the matter is: while people want to heal themselves, eat well, predict well, they may not necessarily often want to do what morality prescribes.
Science became accepted as objective not just because of how good it would be, but because people *wanted* to follow it.
Science, math are more aligned with a lot of what people want. and sure you will find reality nihilists and moral nihilists. There are people who think of science and math as subjective, a fiction of the patriarchy or whatever.
The problems morality has are not unique to morality. The problems are only more present with morality. First, math and science deal with more popular desires and can usually be summed as : ”if you want to …. then the best way to achieve it is… ”.
But what if you prefer a round about way of doing it because you like the smell or w.e? There are still values involved.
Morality isn’t even clear. It is too broad. It’s most accurate to see that it’s just people saying ”that’s how I want you to act” ”if you act this way, I will approve of you, otherwise if you deviate I will disapprove of you”.
People have much more conflicting values in morality than in science.
That is why we more generally follow prescriptions in math and science, and less generally follow or even agree on morality.
Not everyone does follow prescriptions in math and science.