They skimped on the tablet, grabbing a <$100 device for cheap. It should be a ruggedized / semi-industrial device with an expected lifetime as long as the device it controls, so at least 15-20 years.
That would set them back at least $800 (2021 prices: last time I had to spec a ruggedized tablet), which probably means $1200 out of the customer's pocket.
OTOH, they can find an industrial display + a Linux SoM (system-on-module) that can run linux or Android for under $200 in quantity.
Same diff though: no one cared, so they got what was cheap.