I think that using the force makes you stupid.
Think about it. On one hand, you have the hubris-filled easily decieved "wise elders". On the other hand, you have sith, with two members at a time only on the premise that they otherwise would kill each other. What's more, the fact that any Sith lord takes on a pupil doesn't make sense, considering that their core philosophy is the self matters more than anything else, so there is no sane reason to share your knowledge and power with somebody else who, because of that same philosophy, will inevitably KILL you when they learn everything. So either you WILL be murdered by your student, or because of knowledge held back every generation the total Sith lore decreases.
No wonder they always use robes and undergo mental training. By the time they reach master status most force-users must have trouble figuring out how to put on pants.