It's basic math. You start with all stats set to 5 and have 5 more points. So only one stat can be maximized, not two or three, and that's fine. But now, if you set your strength to 8, you have only 2 more points to spend. So, you're basically forced to spend more points into STR than any other stat.
Otherwise, you'll never know when you will find some weapon that suits your character skills perfectly, but you won't be able to use it properly. So, my question is simple: How can STR requirements improve gameplay? I still can't find any logical explanation.
You are not required to use the points on Strength. Ideally in RPG's, PC development should create a "path" through the game. adding [or subtracting] to stats opens some doors while closing others.
If your PC is not strong enough to use the bigger guns, then they should have to use them under an accuracy penalty ... (because they can't control or aim them properly); but if they
are strong enough, they automatically do so under a different penalty (because they withheld stat points from the other attributes to boost their strength). These weapons are a feature that should be committed to to have unrestricted access; their use should come with a caveat. Effective Big Gun use is part of a PC's chosen path.