Why don't some hospital/clinic they automatically issue out ORs for the professional fee of their medical practitioners?

When my mom was paying at the cashier for the hospital bill of my dad, they initially refused to issue out an OR. But after she repeatedly stated that she needs the OR to have it reimbursed, they finally gave way.

At the same hospital, another lady was paying and also requested for an OR since she's only a katiwala of an OFW and that she needs one to properly account the hospital expense of one of their relatives. The hospital then gave her a breakdown of the professional fee written only on a notepad - saying that can serve as the OR.

Another big & popular hospital/clinic where my mom went for an outpatient & dental services also refused to give an OR.

The dentist that I used to go to also doesn't issue out ORs automatically when I make my payments (I used to spend P2000 per visit for my dental treatment then).

Buti pa yung small clinic malapit sa amin, they do give out an OR when they charge a consultation fee.