They probably just don't want to be sued when some Darwin Award candidate manages to set himself ablaze with the stuff. I seem to recall some media reports trying to blame the Minister for Petrol or whoever, when someone ignited herself whilst transferring petrol from one container to another in her kitchen with the gas ring going at the same time.
Yep, I remember that one. The trouble is that H&S now allows these people to get to breeding age and pass on their dumba** gene! Before they would have been weeded out of the gene pool at an earlier age.