(Somebody made a thread earlier which I believe was deleted due to revealing secret sauce point calculator information, which ate my reply mid-composition. So I will share my thoughts here instead.)
I believe that 2+ is priced that way in the points formula to encourage players to instead look to weapons and abilities for strengthening units. I'm not sure if it's the right or wrong design choice but I do know that when you want to guide players to a particular range of choices, you put it on a curve.
For example, say we author a new game (not One Page Rules) where we want players to choose their own Attack stat but to not necessarily restrict them to upper or lower limits. We want them to gravitate towards selecting 7 so we'll implement an exponential cost curve (y=2^(x-6)+4) which silently guides them to select in that range.
In the below graph, the Attack stat cost is non-optimally priced below stat ~5 and starts becoming prohibitively expensive beyond stat ~8. The curve was designed to place stat 7 in the "goldilocks zone".
Players who really want incredibly inexpensive or incredibly powerful attack stats can still spend disproportionate amounts to get them while truly game breaking values are entirely out of reach.