Playing a +2 STR race or+1 STR subrace with a STR class is not playing an "optimized combat machine".
It's common sense. The game recommend this to you.
And since both point buy AND array only give you a 15, with those options you can't get a 16 or higher without matching race and class. And you are stuck that way until level 4.or 8.
I had this problem doing a one shot. I DMed and offered a stack of premades. All 6 players picked the race/class ability matches, noobs and vets alike. Because if:
- you don't roll
- you don't match your racial ability scores with you class primary score
You are stuck with low scores until level 4. And STR 14 dwarf cleric neither looks strong nor plays as strong. And I think that's the other part. The game
stealthily assumes a 16 in your class primary or powergaming 2 14s. The premades in the Starter Set have 16s. The example dwarf in the PHB has a 17. And some of the DMG math runs on a +3 bonus.