Why do high elo junglers not buy boots?

After watching some jungler streams,this is a question that came to my mind.Why do they buy boots after finishing the jungler item most of the time?I know it makes killing camps faster,but on the other side you can not gank as efficent as you would do with boots since you are not only slower when chasing but you also take longer to get from lane to lane.

Would it not be better to get boots as first item?It improves pressure on all lanes,helps chasing down and even if it takes a bit more time to clear the camps,the movement speed should make up the time you are in the jungle plus you can run away more easily if you fail a gank.

Or is it just a personal preference?