He's been building these kinds of devices for almost 35 years; he basically built his business (and supported our family) on the back of Motorola 6800-series microprocessors, and now uses the Freescale S08 series, which is descended directly from the 6800 (8-bit, von Neumann architecture).
To this day, he codes everything in Motorola/Freescale assembly language.
In his mind, it's the only way to keep his code adequately lean, efficient and maintainable. He's never been interested in C, as he thinks (from observing younger engineers using it) it just gets in the way.
And while the coding and debugging process seems very painstaking, the results are excellent. His devices sit out in the field taking hourly readings for months or years at a time, never failing and going for over 12 months per battery change.
Initially I thought he was just stuck in the past and that his refusal to embrace more modern hardware platforms and higher-level languages was a disadvantage.
But now I see how reliably and efficiently his devices work, and how inexpensive the components are (the microprocessors we use cost just a few dollars each), I see it as a huge advantage over our competitors, whose products are much more costly to manufacture, much more power-hungry and less reliable.