Demised, I know what you mean, but it isn't realistic at all. Remember, Fallout is based on realism. Everything you see in some way relates to real life situations and all of the mutagenic things (like mutants and ghouls) can all be a possibility, if nuclear war does occur (the basis of Fallout is post-nuclear life).
The reason you saw swords on those enemies (I know which ones you are talking about, but I forgot their names) was because it was dishonorable for them to use guns. They were some sort of Ninja-Samarai type of clan/gang/cult/whatever.
Anyway, it would be pointless for our guy to use swords because a swordsman stands no chance against modern-day weaponry. If you want close combat weaponry, daggers, knives and small jagged things are best because they are quicker to use in a close combat fight. Try sneaking up on someone with a big Katana in your hands...
Another thing is (and I'm not sure, its just my opinion) that this game wasn't built on the idea of making it look "cool". Although a big sword ninja guy is what you may want--maybe because you think it looks cool or because its more fun to fight that way--it still doesn't fit in with the point of the game. Try to imagine a soldier in Mach II Power Armor with a sword... lol its sort of funny. Then try to imagine a guy who saved the world with a sword... also pretty funny (i know, you'll say that there are daggers, but you never use those daggers after like the 3rd city you visit anyway).
Well... yea... so that's what I think