I think some take everything advertised about the FCD literally and assume guys use it for all those reasons. I don't, I bought my first to try it and see if I could find benefit from it.
...and I did, I do a good job of loading 9mm and I load for shooting practice, accuracy and just because I like to play around with different powders and projectiles.
One thing I found is with matched headstamped brass and certain bullets I could hold the target OAL easily inside a + or - of .001" but with either mixed brass, brass that had been shot a lot and different types and makes of bullets, the out tolerance on length grew to + or - .002" or slightly more. I feel that a length variance such as this will have an adverse effect on accuracy in a semi-auto pistol.
So, I decided to try and back off my crimp slightly in my seating die and finished the crimp with the FCD, this worked very well for me and I continue to load all my 9mm and 45 ACP in this manner, even with the combinations that always held their lengths in the reloading process.
My brass is sized just fine and dandy in my resizing die so I don't need any sizing being done in my crimp die. I also don't beat up or distort my brass during the reloading process so I don't need to bump out any misshape that might occur if I didn't know how to set my dies or my machine.
The Lee FCD works for me and that's why I use it.
Oh, and guys that brag about not needing a Wilson gauge are kind of like a guy bragging that he doesn't need spellcheck, maybe he's a great speller or maybe he's so bad that spellcheck couldn't find a clue on what that guy was trying to spell, so the guy shuts off spellcheck just from the sheer annoyance.