Weapon limits are weak attempts to reintroduce some of difficulty removed by moving to regenerating health by giving the player additional decisions regarding weapon and ammo management. But given most shooters are not survival horror, ammo is never in scarce enough supply for this to actually matter. The only thing this decision really adds to a game is an element of “haha gotcha”, where in a later gameplay segment the player is punished for an earlier decision. You know, picking up wrong set of guns despite lacking the information necessary for him to be able to make this decision correctly; he has to get lucky, or get it wrong once and know what the correct choice actually was when he replays that segment. Pretty much equivalent to blind leap gameplay in platformers. There’s no skill involved.