Bayonets are used both because of tradition and because soldiers need to lug around utility knives in any case. You might then just as well make it possible to mount them as bayonets.

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For a completely different and unrelated idea, maybe you could use bayonets when boar hunting? In Sweden we have just recently started using boar spears as a complement to knives/hunting machetes (while spears have been the modus operandi in France and Germany for like forever). But why lug around a spear when you can just mount bayonets? Many Swedish hunters use surplus military Mauser rifles anyway which readily accept bayonets.

The entire idea of using cold steel when hunting boar is that as boars are very tough, a badly aimed shot might just wound the boar instead of killing it more or less instantly. This makes the boar very angry and aggressive, and with barking dogs circling it at a short distance you don't dare fire again as the round might well hit a bone and ricochet, killing a dog. The thing to do then is to slit the boars throat with your knife while at the same time avoiding being disemboweled by the razor-sharp tusks. Our continental neighbors (who unlike us have hunted boars for more than the two decades they've existed in our fauna) long ago figured out that was very stupid, and as I said, use spears instead. But as most people around here don't have boar spears lying around, bayonets might well have a role to play.

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