Milsurps have full wooden stocks to protect the rifle when bayonet fighting. The bayonet itself is a throw back to 16th century infantry pikemen, like 4V50 Gary says. The PBI didn't repel cavalry with bayonets ever. They formed a 'Square'. A square was an infantry defensive formation against cavalry. A hedge of bayonets that horses shied away from. No square and the PBI got slaughtered by cavalry.
Mind you, a lot of military things are done, just because it was the way it had been always been done. Even as late as W.W. I, the plan was for the PBI to break through the German lines so cavalry could follow through into the rear. MG's, artillery spotters, etc were ignored.
It wasn't until the Canadian General Sir Arthur Currie invented every current SOP(assualt training, maps issued down to section level, recon, counter battery fire, batle rehersals, etc.) for the Canadian Corps' Vimy attack that it changed.
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