Many of us collectors Yup - I am trying to get and keep all of them hence I am reaching the limits as I have dupes of several characters too (I may not keep all of them though as they can get sacked if required). I also use these characters as places to store overflow talisman. I can see why many do not. I would rather just get rid of all spare talisman and have all my strong ones ready to use in the inventory. But a 'goal' was to have enough sets of talisman to make sure that I could eventually have the ideal sets on each character I have (including making sure that the DEF and MR etc are balanced as far as they can be...yeah I know a bit OCD)...but it takes a lot of time!
Hence my roster is usually bursting at the seams onlead up to sac events - I tend to not cash in souls until the sac to keep them out of the inventory (unless I have spaces for levelling up Eddies etc doing farming).
I would imagine there are a lot of players who keep one of each character - maybe I am wrong? I always have - not even sure why but likely because why not!
As others have said they at least need to expand it to keep in line with the wave after wave of monthly character increases. That makes a lot of sense...same for talisman slots and other aspects of the inventory.