I rarely use it but recently directed and edited a two camera corporate shoot with two C300 MKIs for a healthcare company and I have to say, as an editor, it was nice having duplicate time code. It's not hard to sync stuff these days but it's one less thing you have to worry about when deadlines in post are tight. Definitely not a deal breaker for me, I don't do too many multi-camera shoots and when I do, it is often with a big fancy A camera and then two or three Go Pros or mirrorless on gimbal or other B or C camera that can't sync timecode so not that big of a deal. I recently did a shoot with my C200 as A camera and my iPhone as a B camera angle to get a really wide shot and it worked out fine just syncing the two by ear but it was literally for just one shot. I hate shooting events and live presentiations or concerts seems to be where TC i/o is a big factor.
You can sync even GoPros as well:
https://www.timecodesystems.com/syncbac-pro/
C200 conversation heard on set yesterday
Old guy: "It doesn't have time code"
Millenial: "What's time code?"
That is really sad :-(
Especially as time code has never been cheaper and easier to implement than it is today!