Because it includes the modified code from the GPL licensed code and any derivative works, which in many cases may mean the source code to their entire application including what they may consider sensitive IP has to be provided or readily made available to customers who have paid for the software. Further to this any paying customer who receives this source code can make it all publicly available for free which can effectivelly kill the paid software.

I am sorry but no. I spent nearly 20 years working in the control industry and specifically for a global company that provided some of these control and monitoring systems. Tracing food from production through to end consumers has strict industry standards that need to be met in most developed countries. For example FDA CFR 21 in the US and the EC regulations in the EU which all have track and trace requirements. This is key if there are any issues at any point of the supply chain so that the appropriate entities can respond in the interest of ensuring the health safety of the public.

I get the sentiment and the insecure connectivity is pure incompetence, but commercial refrigeration is not the same as consumer refrigeration, with much more complex controls required to deal with managing large energy consumption, irregular and frequent access, variable amount of goods being held, and usually mandatory persisted logging and automatic alarms, sometimes being sent centrally and 24 hourly to meet strict food regulations.