If Google or YouTube has an outage people don't instantly die. Likely no one will be harmed by a bug and it can be fixed and deployed. The same isn't true for a

If Google or YouTube has an outage people don't instantly die. Likely no one will be harmed by a bug and it can be fixed and deployed. The same isn't true for a spacecraft or submersible. Google doesn't need belt and suspenders development, human safety systems usually do.