The straight-ticket option causes confusion, and increases roll off for non-partisan races and ballot propositions. It is hard to implement on voting machines. It is harmful to independent candidates and minor parties.
Whatever one may say about the problems with straight ticket voting, this isn't one of them. Even back in the day of mechanical voting machines, the necessary logic to implement it was fairly easy to design and build, tho it was a maintenance hassle, and that was mainly due to the mechanics needed to ensure that only one candidate was selected for each office. Mechanically, an OR gate is simple. Now that everything is being tabulated electronically, be it by touchpad screen or Scantron sheet, it's pathetically easy to implement