The period of X-Ray bootlegs ended quite abruptly. Some say within a year. Around 1963 - 4, something happened which changed everything - and it was nothing to do with the authorities or clamp downs or censorship. As has so often been the case in the music industry, it was a technological change - in this case, the reel to reel tape recorder. These became widely available and cheap enough to be owned by many people. There was no longer any need for the laborious complicated process involved in cutting music onto x-rays. And you could fit a lot more music and at much better quality on to a reel of magnetic tape.
Home recording with tape became widespread indeed it lasted right up until the 80s ushering in a period of what was called 'Magnetidzat'. Why the authorities did not see this coming is anyone's guess.