Fighting styles are always geared to the situations people expect them to be in. MMA is a combat sport based on unarmed street fights and holding to the ideal of as quickly and effectively subduing an opponent. Fencing, for example, is not aimed at battlefield combat between feudal warriors wearing mail and carrying heavy weapons, but unarmored civilians engaged in honor duels to first blood.

Traditional Japanese martial arts frequently descend from Edo-period traditions re-organized in the Meiji era, and often focus on weapons training. Kendou for example, still focuses on heavily-armored warriors fighting with swords. I don't think that many people think this is preparation for a realistic contemporary combat situation so much as it is lived respect for tradition and knowledge. Traditional martial arts frequently have other goals, as with Morihei Ueshiba and aikido.

MMA tends to market itself as "real fighting", but it carries its own assumptions about the conditions of fighting. It would be as ridiculous to pit an MMA fighter against an armed and armored Japanese kendoist as against a WWII-era GI with a Tommy gun.