This is just a theory, but maybe the purpose of Strength and Intellect is to keep the skills of lower circles relevant at higher levels.
It’s pretty clear that 1 STR/INT will do next to nothing for a skill that has base damage of 5000 (let’s assume single-hit), but for skills that are much lower in base damage, 1 STR/INT increases its damage considerably.
STR and INT obviously benefit more from fast attacks, multihits, and multipliers, but assuming we’ll keep power-creeping to the point where STR and INT hardly contribute much damage increases to R8-R10 skills, they may help keep skills from lower circles useful throughout higher ranks.
Maybe this is what IMC intended for the purpose of STR and INT?

