There was a time.. not so long ago.. when ALL inking was done directly on top of the original pencilling. And, on bristol boards of varying weights.. In some cases, when samples of the pencilling were intended to be saved.. The inker would be required to ink a page, using photocopies of the pencilled pages. Tracing them. using a Light Table..
With the advent of computers, scanners, and printers, and the Internet..
Many pages today, are sent from penciller-to-inker as purely Digital files. The inker can then print these files out on his end, as blue-lined boards upon which to ink traditionally..
Or, he could also choose to ink the files themselves in a purely Digital way.. using Photoshop & a wacom tablet.
In both of these cases, the original pencils would survive the process unscathed. And you end up with more original art, than you would've ordinarily..
Hope that solves the mystery for you!