Why are corded Drills so different from cordless drills?
All of the "cordless" features debuted or were available on corded drills. The biggest factor now is that cordless drills have fallen so far in price that the market for corded is comprised entirely of people who have opted out of cordless. The superior holding power of keyed chucks, depth stops, secondary handles to counter torque, along with the more powerful tool make the corded drill excel at drilling multiple or difficult holes. 

Other features which have remained on the corded drill are because of its superiority in continuous usage. The trigger lock can be handy if you're using the drill as a grinder, buffer, whatever. If you need to use the drill inverted for whatever reason it's easier than holding the trigger with a pinky. Setting the speed via a dial rather than trigger pressure is also preferable there, because you can lock in the slower speed. 

The keyless chuck and clutch common on cordless drills are more user friendly when it comes to rapid bit changes and driving fasteners. The addition of the clutch necessitates reverse, because "only drives screws" is an awful selling point. Driving screws with a corded drill is easy, but breaking out the key every time you need to drill a pilot hole and getting out a screw driver if you need to back out a screw gets old really quickly.