Jungling makes people extreme sloppy. Generally speaking a jungler will fall far behind on the leveling curve AND gold curve because they're not turning the safe farm and surprise into ganks and they also don't try to stack at all which causes more downtime than needed.
People who play Ursa seem to level Overpower/Fury Swipes which is ok if you're just going to sit in the jungle but it's been far better in my experience to level 1 fury then go earthshock/overpower so you get the ballin slow. It turns into kills and makes you better in the long run but people just level OP/FS because they only want to farm farm farm and don't even look at the lanes.
Same thing with Doom. People don't gank even though he is a great great ganker when you come charging out the woods and destroy some bitch.