I checked the Ill. State Bar Assn but they don’t show members. I really don’t understand the info you posted..I know old age, but I assume he was admitted to the bar in 1991 but hasn’t practiced law by his own request. That sounds strange.
That info is from the Ilinois Supreme Court (attorney registration). It’s “the bar” itself, rather than the bar association.
Maybe he’s inactive because there are continuing legal education requirements and other tasks which he is too busy to complete. Or maybe to avoid malpractice liability if he opens his mouth and starts practicing law by accident.