dullonien said it well. To use another analogy, I've done Hapkido for many years, however my biggest criticism has always been that being 6'2'' and over 100kg, that I've often relied on strength rather than technique in my throws and joint manipulation. Which is true, even at competitive level if I don't get the right positioning I'll still execute the move poorly but succeed due to being bigger and stronger. Some players, like dullonien pointed out, stick to what they know rather than risking failing. Say Manu Tuilagi risks a pass and it doesn't find his man, in the same situation he'll next time do what is tried and tested, which means he'll have trouble developing but not risk failing as well.
Nonu is an example of a guy who learned how to distribute well. He's actually now got a very good pass on him and uses it to good effect, which makes him more valuable than he was from 2003-2007 (despite probably being quicker, stronger and better at breaking the line).