Now, is C the best possible tool for these jobs? Certainly not. But it's the one we have and it's got a pretty fantastic track record.
The heart valve code inherits constraints that make C a lot safer: it has an extraordinarily limited feature set, its functional interfaces are simple, it changes rarely, and the time - to - market pressures it faces are dwarfed by other factors like certification and manufacturing.
Consumer software is richly functional, has complex interfaces, changes constantly, and is written under ridiculous scheduling pressure. In that environment, C does indeed give you software that is as likely to enable someone to install a trojan on your system as it is to properly render an image.