[Kerb_]

If you mean the retroreflective stuff, that's because it requires a bright flash to work. Modern digital cameras now are generally good enough to not require flash for a good picture, even in low-light conditions, so paparazzi don't use them near as often.

Clothing or accessories that shine IR are a completely different functionality and while they could be stopped by paparazzi buying better IR filters, that requires an additional cost on top of the camera