Golf Caddy

Question
Why do caddies in pro tournaments have to carry the bag? Subsequently why are carts not used?
Is it against "the rules" (what rules) and why???????

Answer
hello keith.  its more of a tradition for a caddy to carry a bag and i am sorry that i don't have an exact answer for that.  but i do know that the use of carts is prohibited.  
its just in the rule that states pga members are not to use carts and that includes their caddies.  there are few exceptions made to this rule.  tom watson's caddy, bruce was sick physically and needed assistance on the course.  a golf cart was granted and he was able to get around the course with that.  i also know this one player who is physcially incapable of walking a full round.  i forgot his name but there is a debate reagarding this situation about whether they should allow him to use the cart.