For me, they actually have. On a regular basis, I’m pretty much testing eyeshadow palettes exclusively; like there are a few times a year when a brand might drop some eyeshadow singles (NARS reformulation) or I try a new range (Sydney Grace) but the majority of eyeshadow products I test are from palettes. This results in less experimentation and less time spent figuring out what to put together–sometimes that’s a good thing!
Sometimes there is a challenge in trying to produce two more dissimilar looks out of the same palette to show its versatility, though. I used to be all about singles and loved to reorganize them in my freestyle palettes… but these days, I don’t have the patience/time/effort bandwidth to do much there. I find I reach for a great palette over trying to mix and match singles on that rare off-day (which is often just me putting something a little more neutral on for photos, so I still need something quick and easy!).