[Richard]

The reason that we use DOT fittings throughout the coach is that any air leak has the potential to impact the braking system. In my opinion, DOT fittings are just as prone as hardware store fittings to leak, but the materials and construction are generally much more robust than the hardware store fitting, making the DOT fitting less prone to a catastrophic failure such as fracturing where the threads meet the body.

Seems a little far fetched, right? Yeah, till you have had one of the garden variety jobs shear off as you tighten it. It made a believer out of me.