It all started for me in the late '70's after seeing so many pros putting DiMarzio's in their guitars. Although I was only playing Japanese LP copies at the time, I just had to try them, so got myself a set of DiMarzio PAF and Distortion pu's and put them in my Northern brand sunburst LP copy (the made for Canada mkt ones w/maple leaf fret markers). Think I also put Grovers on it too, IIRC. Wish I had that guitar back actually - was a pretty decent sounding/playing LP actually. I don't always change pu's however - only if I feel the end result will justify the cost/bother of swapping out.