Some of them are old, which is sometimes a sign of sloppy maintainers.

But only sometimes. Some people grow angry when PRs are rejected, so some maintainers leave PRs "open" forever instead of rejecting them formally.

Because (imho) it reflects project hygiene, health, priorities, and attention. Which I'd hope is a higher priority for something as important as a distributed network of proxies for a critical messaging service that oppressive regimes are blocking.