Why?
I had a 2011 E90 M3 and loved the DCT. I had come from driving an '03 S2000 for 8 years, so I "get" the manual thing but would take a good DCT over a manual any day.
Well the first reason was that my car has some jerkiness at slow speeds which seems to be hit or miss among other M3 drivers, it isn't terrible or anything but it sometimes felt clunky which didn't inspire much confidence maneuvering in my nightmare of a parking garage.
The second reason just had to do with the way I enjoyed the car. DCT is definitely fast and if I was racing competitively I would have enjoyed it more but when I was on a track it was for fun and I felt like I would have had more fun with a manual. Elsewhere it didn't really provide a bunch of benefits without doing things you're not supposed to do on normal roads
It's not a bad middle ground solution, just maybe not a compromise I would make on a car that's supposed to be a fun toy.