Because for certain professions income is reliable but not set to a 14 day pay cycle.

Could be that OP is a freelance author and is paid depending on when stories are picked up, or is contracting for multiple employers and has an irregular payment schedule depending on their invoicing.

Not everyone conforms to the same set of employment/fiscal assumptions we (here meaning "educated white collar US tech workers") may have.

Why does this matter if all parties involved were satisfied with the arrangement?

I have my rent set up with automatic payment, and the date the payment actually goes through varies +/- five business days. My bank even warned be to set it to go through a week early.