It's possible no one bothered attempting it with something that was more or less impossible to mount on Protos anyway if you wanted to also have minor luxuries like armor and actual movement. The prototypes were attempted, were still impossible to use for any practical purpose, but no one bothered adapting the techniques back to standard weapons because, well, they were still uselessly impractical. Personally, the ER pulse laser bothers me less than an LPL would.