Title says all, for people who have been here for a while, but I'll go into the finer details for those who did't.
the game used to archive your save files in a different manner. it wasn't just "One subfolder for each character", but you had the ability to create several distinct "Player profiles", each one with its own subset of save files.
On a surface level, not the biggest difference (and in a couple of ways the current one is even an improvement: now you have every playthrough generating its own subfolder without even doing anything), but in an ideal world I'd be vocally in favor of a system merging both solutions in one.
Why? What does it change in practical terms? Well, MODDING.
The old system allowed the player to select and enable (OR disable) a certain configuration of mods and to keep it active only on one specific profile.
You could have concurrently a playthrough with a certain selection of mod active, another with a different one, and yet another where you kept the game "vanilla".
Conversely, the current system denies this flexibility, because your selection of active mods is automatically extended to ANY savefile you are going to load.
P.S. Please note that I'm not being forgetful. I'm perfectly aware that this is a (rewritten and reworded) copy of a similar thread I started "Suggestions and Feedback", but after some thought i decided that this is probably the most pertinent place where to highlight the issue, given that modding is the most affected aspect of the game.
