Saying why doesn't Dante keep his weapons is like saying, Why doesn't Meagaman keep all his powers? Why doesn't Link keep all his equipment? Why doesn't Samus keep all her upgrades? Why doesn't Sora keep all his skills? Why doesn't Snake keep all his Camo's?
It's just how video games work, they aren't going to give you your characters at the super-pwerful level they were at the end of the last game at the beginning of the next. It makes the game too boring. Besides, remember, when it comes to why Capcom didn't give DMC1 his DMC3 weapons, is because at the time DMC1 was released DMC3 and it's weapons didn't exsist. They never knew there'd be a prequal.
KA: You are right about that Lobuk but you never said I was right about DOS.... *pouts* tee hee I jumped in your box....