Sure we are, at least pretty close.

Commercial avionics software developed to DO-178B standards calls for reams of requirements, verification tests, compliance to process, internal quality reviews, external audits, and sign-off by FAA representatives.

A one-line code change can take days to implement, and might not be released to "users" for months or years.

But the software is extremely robust.

If we wanted to engage in the same level of software engineering for all software, we could. But we don't want to. Developers don't want to, and users don't demand it. If an iPhone game crashes, who cares? If a productivity application crashes, you might have lost an hour's work, but it's probably not so annoying so as to warrant a couple orders of magnitude more cost associated with the software.

But if a software failure could kill people, well, that's different. It's worth spending a huge amount of time to make it perfect.

Avionics software can be so thoroughly tested because it is thoroughly designed up front. You know exactly what it's supposed to do. Much less-critical software is designed in a more ad hoc fashion; or there might not even be a design at all! How much software has been organically grown, starting with an idea and hacking on it until it seemed to work?

If you want to thoroughly test that, you have to go back and thoroughly state what it's supposed to do.

It's quite possible, but by and large it's not desired enough to make it worth actually doing. I'm not sure how this could change, or even if it should change. Instant bug fixes on web applications are cool, even though they come with the risk of having broken something else...