Reason behind keeping Date of Birth mandatory by default while hiring Contingent Worker?

Summary:

We are implementing Oracle HCM where we saw that Date of Birth was marked mandatory by default from Oracle delivered product on Contingent Worker hiring page. We want to know is there a reason it was done. We are checking this because before we make it nonmandatory, we want to ensure we are not breaking any system functionality by doing so.

Please help if someone has answer to this.