Earlier quoted context omitted.
Some people have claimed that in my organization. I think that can work for library code, and particularly libraries that are used in many different places. But once you're talking about a service, or code that is only used by one service, then you need to have an owner (or a team of owners). If you still think there's no owner, then ask yourself who is going to get woken up at 2AM when it breaks, and that's your own…
the team owns the code. the whole team. whoever is oncall gets to wake up at 3am if there is an issue.
IME even in small organizations (<20 engineers) it's very easy to end up not knowing enough to debug everything, and your on-caller basically becomes a smart router. ie, they can debug enough to figure out that it's a DB problem, and then wake up the DB guy. This becomes really annoying for the on-caller, so there's an impetus to have more focused paging groups, and now you're back to having owners for services.