>Why would you actively choose a position that would be considered anti-social instead of a position that would be considered pro-social if they have the same objective grounding?

Because one positions imposes significant costs and restrictions, leaving your life significantly worse off.

Paying taxes to support the welfare of others is pro-social, but it means that I am laboring twice as much, instead of relaxing with my friends an family. It means that I am paying for the children of others using resources I would rather devote to my children. Why should I sacrifice my wellbeing for someone I don't know, and might not even like if I met them.

Many behaviors that fall under the Pro-social labor hurt the individual and benefit others.

If they are actually beneficial to the individual, they wouldn't need to be compulsory or the pro-social rhetoric.