Compulsory means that you have to do something.  I have seen many players play not wearing shin guards, obviously it helps safety, but compulsory means that the referee should not let them play if they do not have them on, but they are nonetheless playing.

Why are the referees and fifa staffing allowing them to play?  Because the sport is fixed, all about money and sex, Swiss banks

under the IFAB Laws of the Game, shin guards are strictly compulsory for all players. They must be made of a suitable material, provide a reasonable degree of protection, and be entirely covered by the player's socks at all time