jacob says that he can't write much of what has been said and done because it's difficult to write on the plates. it would take forever to just write it with a pencil much less carve it into metal plates! jacob says that they will take the time and trouble to write those most important things on metal plates because the things on plates will last through time. they have paper and use it to communicate with each other, they use it for scriptures etc. paper is not really meant to last the centuries though. just the really important stuff is being engraved on plates with the intention of it being read by future generations.
we had a little example of this done for us in seminary. our seminary teacher made copper plates, ( i assume he bought some sheets of copper and cut them down to the size of the small plates. around the size of a large recipe card). he gave us some tools to write with and a list of glyphs. he told us to write what was most important to us. we had to write it in egyptian letters on the copper plate. we only got one plate and had to do it all in one 90 minute class. we wrote on paper first but then had to condense it down. then we had to press it into the plate. that was not easy! imagine gripping your pencil really tight and then pushing letters into metal. our fingers were sore. we ended up with only a few lines since the plates were small, (we got the small plates of nephi). it was one of the most spiritual lessons we ever had. several of us had personal prophecies revealed to us. our teacher did too.
if you have never boiled down your testimony to the bare bones, i recommend it. in your journal, write your testimony. then condense it down to the most important things. in just a few lines, tell your future generations what you want them to know. it is an amazing experience.