Why do SPECIAL can't go below 4?

I was wondering why the rules say SPECIAL can’t go below 4 for the PCs?

I mean, a stat below 4 would still lower the chances to get a success, so why the hard limit?

I discussed this elsewhere:


Isn’t that low end of 4 kinda baked into the 2d20 system too?

On a game-by-game basis we’ll build a minimum value into character creation, but sometimes it’s higher if the game assumes a high level of base competence (such as in Star Trek).