It can be easily added to ephemeris software. Generally, I use a value of 25 percent or 50 percent. The uncertainty is displayed on the third line of the ephemeris' header, rounded to the nearest second, right after the age of the elements. Mike McCants has implemented a prediction uncertainty calculation in his Quicksat program, so I am not the only one to have dealt with this problem. In closing, I wish to point out that although satellites are man-made objects, representing some of our most advanced technology, once in orbit they are subject to the forces of nature.
Uncertainty is part of the sport of our hobby.
To be successful in the pursuit of our quarry, we must know its habits, and the habits of nature. I do not mean to imply that prediction services should necessarily include old element sets, but they might wish to consider amending their software to compute the prediction time uncertainty, and provide their users with an explanation of how to make use of it.