Incenjucar
Legend
IMO the current 5E playtest material does not stand as a separate (and confrontational) playable game on a battleboard, nor does it stand up to either DM or players wanting to use the rules to their full extent for advantage.
The story-based reasons for not squishing wizards, not having rank-rotation in the front rows etc, are best maintained without the grid, and with additional effects, not codified in the published rules, limiting choice narrated in by DM and players. As soon as someone reaches for exacting measurements so they can get some rules to back up a play, it's time to start looking for (or at the moment, wishing for) the tactics module.
What story-based reasons for not squishing wizards?
The reason to not squish wizards is entirely meta-gaming on the part of a DM from what I can tell. Nobody in their right might would go after the fighter when there's a wizard or a cleric that's just as easy to get to.