You misunderstand. Service worker traffic is invisible, unlike loading an image and generally speaking can't be governed, unlike visible elements.
Loading 1-10MB JSON might drain a significant portion of mobile data. It could take a long time, meaning it may need to re-start it a couple of times, due to, say, a flaky 3G connection.
I'm curious on the why - unless this is an announced feature, I don't think this should be an automatic process and should only be done on user demand explicitly.
I agree with you, there are several settings avail to control what is optimized, it’s typically enabled on faster devices/connections at work. I would be upset as well if a site naively used up a connection in the background.
Loading 1-10MB JSON might drain a significant portion of mobile data. It could take a long time, meaning it may need to re-start it a couple of times, due to, say, a flaky 3G connection.
I'm curious on the why - unless this is an announced feature, I don't think this should be an automatic process and should only be done on user demand explicitly.