It avoids error-prone text parsing. Text Credit Reports Credit bureaus can format reports and send them to you as text. This is the TTY method. The TTY method is not suited to any application that needs to actually use the report data. They don't publish technical specifications for them, and they reserve the right to make layout changes without warning.
Data arrives in packed, predefined record layouts.
It is near-impossible for human eyes to read, but the computer can handle it quite well. As the bureaus add new data elements, they do so with strict version control, and in a way that protects the integrity of existing systems. For example, when the bureaus went to 4-digit years, they did so by adding data segments to handle them. Applications that didn't need the 4 digits could count on the 2-digit year fields remaining where they had always been. Fixed length record layouts are incompatible.