Benefits work like this:
CRJ - everyone has the option to pay for delta and united. This extends space available travel to one's immediate family.
Depending on your domicile you may have the option to pay more money for different airlines.

Embraer - pay money and get united but not delta.

Short answer: pay money to hear your parents complain about being inconvenienced by 90%+ load factors.

Int'l DAL travel is sweet though.