That is just combinatorial explosion of fairly small number of features. I took a peek at the example you provided, and drilling down there seems to be for example 39 SKUs for PIC12x615 chip:
* Two voltage options (although why on earth do they need 2-5.5 and 2-5 separately?)
* Two main packaging options: tape and tube, and tape is furthermore available as full reel, digireel, and cut tape
* Three different temperature ratings
* Five different device packages from tiny 3x3mm DFN to full-sized DIP
So already from these fairly simple options you get total of 2x4x3x5 = 120 different combinations for essentially the same chip. So they don't quite have all the combinations, but there are few outlier options and overall the combination coverage is pretty wide which explains the inflated SKU count. I'm not sure what conclusions can be drawn from this exercise besides that Microchip seem to be willing to provide their chips exactly as customer wants them.
* Two voltage options (although why on earth do they need 2-5.5 and 2-5 separately?)
* Two main packaging options: tape and tube, and tape is furthermore available as full reel, digireel, and cut tape
* Three different temperature ratings
* Five different device packages from tiny 3x3mm DFN to full-sized DIP
So already from these fairly simple options you get total of 2x4x3x5 = 120 different combinations for essentially the same chip. So they don't quite have all the combinations, but there are few outlier options and overall the combination coverage is pretty wide which explains the inflated SKU count. I'm not sure what conclusions can be drawn from this exercise besides that Microchip seem to be willing to provide their chips exactly as customer wants them.