This was a concept that developed as a result of an Instagram post that received lots of replies to someone who asked if he had plastic surgery. Someone just assumed that his good looks could not be natural and that he must have had some work done on himself with plastic surgery.
Beckham himself replied to these comments, but never affirmed this theory nor did he reject the idea. Apparently he took it as a complement. Others think that his looks just come as a result of the lighting and camera work. Many people seemed to defend Beckham saying that he must not have had any surgery and the his looks are natural.