Maybe there's "some" people out there who like to do the entire soup-to-nuts process because they like hard work?There is no need for me to carry DSMB and reel/spool unattached. I’ve always carried them already rigged together and I see no need to change at this point. My regular buddies also carry them already attached.
Me, I hang the large reel and self-inflating CO2 cartridge SMB off my waist belt. Reach back and it's all ready to launch.
The spare's in the suit pocket rigged up with the spool and SMB, again ready to go.
Can't be doing with additional faff at the end of a dive.