A vexing question is why systematic quality assurance and formal methods, despite
all their advantages, are  not used routinely in software development.
Other engineering disciplines use their systematic quality assurance and formal
methods in producing routinely reliable products.
Perhaps the difference between the other engineerings and software engineers lie 
in the warranties producers must give for the products and the liabilities suffered
by the producers for malfunctioning products.
It is argued that software engineers would be more likely to use formal methods 
routinely if they or they employers had to guarantee their software and could
be sued for damages caused by their malfunctioning software.