What’s the point of a flail if it doesn’t even give me a small advantage against shields?
Every system has to decide where to draw the line on the prioritization of realism versus simplicity and speed of play. On one extreme you have the “one page RPG” system where you have exactly two stats and everything uses one or the other, rolled on a single D6. About two thirds of the way to the other extreme you get “Pathfinder has a rule for that,” with some systems going into truly absurd levels of detailed minutia in ways that vary from being mote or less mechanically consistent to the old school D&D method of the designers pulling a random table out of their ass for every new thing they don’t have a rule for yet and filling it out with whatever nonsense comes to mind in that moment.
I care less about realism than I do about having interesting decisions to make. I think it’s a really big challenge for game designers to make it fun and interesting for players — even highly skilled ones who love to strategize — without the game bogging down by having too many dice rolls/decisions to make.