My issue with telemetry is that 99% of software ends up not using it. Why have it? And definitely don't have it by default. Your users will come tell you what they want, making telemetry useless, especially when it's an OSS project you're mostly building for yourself.

Except that telemetry can give you more complete (and foolproof) information than what users report. But yeah, that could also be solved by having debug info that users can attach to their report, the app doesn't have to "call home" for that...