I work on dev tools at my company. Telemetry really helps a ton to figure out if you're prioritizing the right things and if changes that you made are really for the better

Opt-in, or opt-out?

For the company there’s no opt-anything, its internal tools, of course we need metrics, and presumably you have nothing to hide with your work :) I’ve become a lot more tolerant of telemetry since starting to work there, because I see the use. If you really care about privacy (as a company/provider), you can anonymize and aggregate the data and still get nearly all the benefits, but I can totally understand why people put telemetry into their product, including opt-out only