Strongly disagree unless/until the attributes are adjusted so that there aren't uber-stats and correspondingly obvious dump stats. And even if so, it still doesn't really make sense why adventurers would be getting weaker (less intelligent/wise/charismatic/hardy/dexterous) the more they adventure.
Setting stats lower than 8 should either be allowed at character creation or only allowed through in-universe deals with e.g., hags, devils, warlock-type-patrons, cursed books, etc (ideally at a steep cost: e.g., gain 1 point at the cost of 2 or 3 points).
And if you messed up your stats so badly during character creation that you need them changed, then you should work with the DM to just change them/change your character.
