Just so it's clear, I meant specifically the '.bashrc runs "screen -DR"' part, ie automatically going back into the screen rather than needing to explicitly run screen -DR like I used to. (I don't seem to be able to edit my original comment at the moment.)
That's not something screen-specific. You can put whatever you want into .bashrc and it will be automatically run each time you open a new shell. pseudonym just suggested you could use it to automatically run a screen command.
Multiple terminals in one session was more critical back when we were using dumb terminals and whatnot - where you couldn't multiplex locally.