[MakeshiftWalrus]

The short answer is:

Everyone is playing rock-paper-scissor in mechanical combat.

At some point, scissor got tired of losing to rock, so it picked the best choices available to it, equipping the best gear, and the best combat style of the given time period, and thus became an atomic pair of scissors.

Then people saw how well those atomic scissors were doing, and copied it.

It was never that we didn't have options, it was that the atomic pair of scissors were too good not to run.