What do service workers restrict as compared to the previous model?
It's a headache early-era iOS developers are familiar with, but this move is basically Chrome team saying "We've watched the community try to implement responsible resource handling, and they suck at it, so we're taking some of their choices away so that the browser can manage resources for the user." Because battery matters.
Mostly this boils down to one thing: there needs to be an alternative to service workers and there are tons of legitimate use cases for long-living background pages or workers. I think by this point everyone agrees on that, the question is when this alternative will be made available to developers. It’s only 3 months until the deadline after all.