I live in neighborhood that went up fast during the pipeline boom of the 70's, so there wasn't a lot of quality effort. I am super thankful that my Dad talked me into blowing in a bunch of extra roof insulation (and maintaining the airflow) right after buying my place. My neighbors' houses have ridiculous icing issues but mine is pretty much ice free.
Keeping a roof system breathing is completely lost on many DIY'ers.
All my life I've had homes in heavy snow county in Alaska and NW Montana and never had a ice dam on one of them.
Properly insulating and ventilating a home in the south is every bit as important. Summer heat build up in attic spaces will cook asphalt shingles from the bottom up shortening the life of them considerably. Moisture trapped in these non-ventilated spaces creates rot, mildew and mold.
Then there's the spray foam guys....
