Most of the SCI game is the class system, the inventory, the control lines, the ego, the dialog boxes, the movement, the doors, switching rooms, etc. However, the parser is one of the very few parts of the game that is part of the interpreter. SCI games with a parser use an INCREDIBLY intelligent and complex parser system (see the FreeSCI docs). There would really be no way to implement a parser like that in SCI1 games. LSL7 has an "enter verb" thing, but that's about as far as you'd get.
The only way to get a good parser in SCI VGA games would be to hack the SCI0 engine, which I am not going to do. I've got so much to do with SCI Studio EGA, SCI Studio VGA, the second EGA tutorial, the VGA help file/tutorial, and the VGA template game, it's really not on my list.