Yeah it is harder to play fast using string skipping, but if you're just going for speed then play nothing but C major up and down. If you want to make music, then trying to introduce string skipping ideas can add wider interval interval jumps and hopefully make your lines mores interesting. Being able to play string skipping lines (especially ones that aren't just simple pedal tone things) can add a different flavor, and if you are going to be playing shred, where it's more about the overall sound that a guitar part creates, rather than traditional melodies, well wide interval lines sound different from scalar runs, and different from sweeped lines, make sense?