What's worse, how many shortcuts like this get buried in walls every day? I've opened up old work where a nail was driven straight through a romex line, or rodents chewed the insulation to shreds. An AFCI would trip the second that damaged wire tried to arc. Skipping them means you're just hiding those future sparks inside the walls until they get hot enough to ignite the framing. It's literally putting a slow-burning fuse inside the house.