I get what your saying.....they aren't exactly putting their "money where their mouth is" in terms of the nearness of Armegeddon are they? But you can't blame them for wanting to improve their day to day life, especially when on some level they know based on past failures, the New System probably won't come in their lifetime, no matter what they might say outloud.
The thing is, there is risk of ones life involved in these procedures. We know a JW woman who had breast augmentation and ran into a snag over the blood issue. She didn't stop bleeding for several days after the surgery and her doctor was pressing her to take a transfusion. Fortunately the bleeding stopped but can you imagine losing your life over something like this or having to enlist the help of the Blood Liaison Committee about a surgery that maybe you didn't particularly want anyone to know about ?
I think they figure that in the New System, Jehovah will remove their implants the same way he'll remove the hip implants, heart valves and dental work that others have had done. I always wondered what people with Dentures will do while their teeth are growing back ? After surviving an event like Armegeddon and the Tribulation, I suppose they figure this would be the least of their worries.