I don’t disagree with your point — however apple only charged for the early iOS updates on the iPod touch. And they only did it to comply with the Sarbanes-Oxley Act — which required that if you upgraded a device not on a subscription, you had to charge.

They stopped doing it after they lobbied congress to change the law.

https://www.macworld.com/article/189247/ipodtouch-3.html