Brake Hoses, Lines/piping, And Fittings problems of the 2001 GMC Sierra 3500

While driving I had my brakes fail, the pedal went to the floor. It was a result of a broken steel brake line under the drivers seat. What I found when I looked under the truck was all the lines that went to the abs unit were badly rusted. One of my coworkers had the same problem on his 2001 GMC suburban but he chucked it up to all the camping trips he went on where he left his truck parked off road. My truck however only has 30,000 miles and it has never been taken off road. I also flush the brake fluid once a year as preventative maintenance, so they can't claim they rusted from the inside out. I drive my truck every day to work about one mile away. My driveway is paved and the parking lot at my place of work is also paved. I don't pull any heavy trailers or do anything else that would contribute to the line failure. I am not putting down gm products because all my vehicles are gm vehicles including two antiques. One a 1955 chevy which had original brake lines until I did a disc brake conversion several years back. The other a 1970 chevelle which is currently a restoration project but the line are still original. There is obvious a problem with the material used to make these lines. I was researching the problem online and it appears that there are to many other people with the same problem. Also gm no longer sells the lines which makes it a much more troublesome repair. I also don't own a boat, jet ski or anything else that would require me to put my vehicle in salt water.