Seriously though, name a single D&D campaign .. EVER .. where you level up from 1 through 20 in a single story arc.
I thought you guys wanted authentic D&D?
If we're talking table top D&D, indeed, almost never. If we're talking video games, Neverwinter Nights 2's official campaign included progression from 1st through 20th (typically rarely hit the cap, usually tapered off between 15-20, but it was available and functional).
I'm fine with this game capping at 10, but it is fun to be able to go into those high levels with a video game since it's, as you say, pretty darn rare to table top.