Let me start by noting that while both knees are currently original equipment, replacements are closer than I would prefer.
Unfortunately, stages where kneeling is required are a standard part of IDPA. Every sanctioned match I have ever attended has at least one stage, usually more than one, that requires the shooter to take at least one knee. Most local matches seem to also have at least one stage requiring the shooter to take a knee. Therefore the kneeling portion of the classifier does represent a skill that every shooter will be required to use in a match.
This past summer, a local match included a stage that required the shooter to take a knee and then "pie" around the low cover in order to be able to engage all targets. The stage started with the shooter seated in a chair, after which the shooter need to move behind cover and engage the targets from the kneeling position. For me the movement while on my knees presented a real safety issue, so I engaged the first target from the chair and then took the 3 second penalty for the remaining 5 or 6 targets. My time was much better taking the penalty that what it would have been had I been forced to complete the stage from my knees. Some shooters on the squad were frustrated that I got a better score by taking the penalty, while I was frustrated by being deprived of the opportunity to shoot the majority of the stage. Personally, I would like to see IDPA mandate that all stages requiring the shooter to take a knee, also offer the shooter a second option to complete the course of fire from a non-kneeling position. If I ever found myself in a real life self defense situation, taking a knee would be an absolute last option. In fact, I would probably be better off exposing myself to the bad guys rather than handicapping myself by taking a knee (or two) in order to take advantage of available low cover. USPSA forces the same type situations when they require the shooter to engage a target through a low port, or under a barricade. For us old guys steel challenge and ICORE offer the best chance to be competitive.
I still enjoy competing, but have come to grips with not being truly competitive due to physical limitations, so all I can say is go out and have fun.