Do you like your ISP being able to inject commits into your repo clones? There's nothing wrong with using HTTPS.
There’s a large set of “I don’t care” style projects where I’m just looking to grab a copy. So even if my ISP (or some nefarious jerk on the same WiFi) could MITM, I don’t care. Plus, I’m not aware of any attacks like this because of the whole git checksum thing it’s harder than injecting into http traffic.
For stuff I care about, I log in.