It depends what kit you're refering to, as those four you mentioned are all fair kop (in fact, anyone who thinks a Mouthguard souldn't be manditory kit either hasn't ever played or has no respect for how dangerous the game is).
On the other hand, kit like forearm pads serve as little more then a cheep marketing ploy for the gullable.
I think some of the gear such as head guards are almost becoming as useful as mouth guards in some respects. The amount of players you see suffering from concussion and other head injuries these days could be mostly avoided with the use of headguards.
Of course i don't want to see rugby become anything like the NFL in terms of protective gear but i feel that if players want to try and protevt themselves whilst playing, the option should be there.
Im sure no young props, hookers or second rows want ears like martin johnson or graham rowntree lol.
mouthguards are a must have piece of kit, as i mostly play prop and have a bad shoulder i always wear shoulder pads aswell but i feel it should be up to the individual player to use whatever kit they want to
Hey, rugby players have the freedom to choose what kind of protective gear they would like to wear, suited to their own need. Mouthguard is a definite must, and believe me, nowadays atleast a shoulder pad is needed for highly competitive club/international games...