I think a lot of that is changing due to the rise of Linux in embedded systems. Many more traditional software engineering concepts are becoming mainstream in embedded.
And for embedded in high value (hundreds of millions of dollars) or human life, I think there has always been lots of proper discipline and engineering process.
I was mostly talking about stuff that runs on much smaller CPUs that have from a few hundred bytes to a few tens of kilobytes of memory. Those kinds of devices are important for applications where you have extremely tight power constraints (like powering stuff off a coin-cell battery for two years etc).
And for embedded in high value (hundreds of millions of dollars) or human life, I think there has always been lots of proper discipline and engineering process.