Why change the habit of a lifetime?
I guess its more fun that way, but when you have won 2 races throughout the year (Im talking about Astana, not Lopez!), you might wanna try to win the races youre actually capable of winning.
Of course, Lopez could channel his inner Santi Perez and take off on Sierra Nevada, gaining multiple minutes, and winning the Vuelta, but my bets are he gets pulled due to his business with the Medellin-cartel, throws a tantrum because Nibali is riding well or gets DQ'ed because he wasn't too fond of a random spectator and decided to live up his nickname.