Actually he does. From SI Bear digest:
"He's often been criticized for an inability to properly handle the pass rush—he'll turn into it instead of sensing the heat to run away from it."
From bleacherreport in 2012 (only Dalton's second year, but tendencies are hard to overcome):
Dalton knows the pass rush is coming... To diffuse this, Dalton goes with a play-action fake.
No one bites on the play-action, but Dalton still finds himself with some time to make a play—and an open receiver to his right. Dalton's not looking at him, though.
The pocket starts to collapse. Dalton is thus running out of time, but he could also try a desperation dump-off to running back BenJarvus Green-Ellis, who is to his left.
Instead, Dalton takes the sack. He doesn't throw the ball away, and he doesn't target his two open men in short yardage. It's like his brain freezes and he just stands there and takes the hit and the six-yard loss.
Dalton's always been rather poor at handling a good pass rush, and with this line he'll certainly get that. Maybe MM and KM can call plays to neutralize the rush - screens, play action, quick slants, etc. We'll see, but what we have to hope we don't see is the same Dalton Cincy saw for years...
Instead, Dalton takes the sack. He doesn't throw the ball away, and he doesn't target his two open men in short yardage. It's like his brain freezes and he just stands there and takes the hit and the six-yard loss.
Only change in the offense will be that we score even more points per game. 
as long as the OC doesn't go all soft and conservative because "oh my we only have a backup now!" Hopefully, if the Giants game is any indication, these coaches gotta be smarter than to play "down" for Andy and not use our main big battle weapons which is the receivers because our D will still be giving up 30-ish points per game and relying on Zeke for 40 carries into a brick wall ain't gonna stop dat unless their leaving big holes open for him. Then take dat!! 
