A possible reason is that it won't happen in git, simply because separate branches aren't sufficiently painful to motivate sharing that single hot mess HEAD. I

A possible reason is that it won't happen in git, simply because separate branches aren't sufficiently painful to motivate sharing that single hot mess HEAD. I used to work in a team where it felt like I was the only person who ever thought about these things and it was quite impressive how the switch from SVN to git completely flipped the path of (supposedly) least resistance: from separate branches only as a last ditch option for the most desperate situations to happy unbounded parallelism right until the (supposed) delivery day.