Cad means Computer added drafting which allows the user to set preferences for many standard items being used over and over again in different drawings.
Example: An exterior wall Using a 2″ x 6″ stud system, has 4 lines and a pattern in it to call out what type of wall it is. For the computer to draw the wall takes only 1-2 seconds.
Now you can place windows and/or doors into the wall at you choosing.
While hand drawing take longer and are not as accurate.
When you have to a redraw of the same print you are smudging your work for just moving a window 6″ or adding a door.
What a hassle.
I’ve worked with Architects before and with Draftsman (lumber company supplied plan drawers) both type of print makers do make gross errors.
From missing load bearing points to making the hallways to narrow, and stairways are almost always screwed up.
Using a cad cuts down a dumb mistakes.
A good builder has to be able to read and understand the prints as they are drown.
IE to be able read between the lines.