Tires: Tire Repair, screw holes, steel belts

Question
Why is it that shops do not repair tires with Fix-a-Flat in them?  Nothing from the Company says that the fix is permanent and they recommend having the tire checked by a tech.  I had a tire that I used it on to get me to a tire store and the place said I had to replace the tire.  Nothing else was wrong with the tire.  

Answer
Hello, John
Fix-a-flat is for like you said to get you to a tire store ASAP. What happens is this stuff smeers all over the inside and some of it is forced out at the opening. Thats what stops the leak. I really don't know why the tire store could not fix your tire. It depends on where the hole is. Most of the time the object that caused the damage also cut the tire cords, if in the sidewall. Are may let water get to the steel belts and cause them to rust, when in the tread. I have never used fix-a-flat myself, but I have bought the do it yourself tire plugs at Autozone or Advance Auto. They seem to work very well for nail or screw holes in the tread.

Sorry I could not be of anymore help
Jack