I don't know and I haven't played in years. But perhaps it is to make cyberware more interesting than just tier 1, tier 2, tier 3. In reality everything has some trade-offs, the more performance you squeeze out in one metric, typically you're going to degrade the others. E.g. lighter means less power.
That way you have to make decisions about what stats you value more than other, which I would argue makes it more interesting.
I Kenshi you have legs for speed, legs for damage, legs for tanks and also balanced legs. And depending on how modded your game is you also have tiers of each of those.
You can make insane scout builds that literally just outrun everthing, but are as fragile as a fly. Or go full on slow tank.
I think that system is much more fun than just having a boring progression were each is just better than the last. That way you actually have to make decisions and not just the pointless hehe number go up.