While it may seem like a further penalty to only have 1 card after an Epidemic, I think it is actually a benefit. Drawing another card would just shorten the game that much more. With 4 Epidemics, you would loose 2 full turns over the course of the game; with 6 epidemics, you would loose 3 turns. I haven't played my copy yet, but that seems like a lot of valuable time that you would loose if drawing a third card were permissible.
The deck limits the time you have to find cures, but the rate at which you can find cures is strictly limited by the number of cards you are able to draw. Drawing a third card would not cause you to find cures any later relative to the end of the game through card draws. It would just cause you to find cures earlier relative to number of infections.
In either case, you don't get an extra card when you draw an epidemic.