The decision to increase the inventory was pretty easy. More slots = more building potential. Previously, a house could take about 2 minutes to build, which was a problem. I don't want houses popping up everywhere, and I also want people to cherish their homes. What's a good way to do that? Make houses more costly.
Increased inventory space also allows more room for activities. You'll no longer need to return to your house every 5 minutes to place your stuff in a chest. Sure, it may come at a cost of reduced realism, but this is a game, not Survival Simulator :P
Here is a preview of the new inventory space (GUI is a placeholder):