You just roll back that one service and every other service picks up the change automatically. Doing the same thing with shared libraries requires redeploying

You just roll back that one service and every other service picks up the change automatically. Doing the same thing with shared libraries requires redeploying everything that is dependent on the bad library (i.e. hundreds of containers instead of two or three). It's not necessarily that one model is better than the other just that using a hybrid approach often means having the issues of both with only a few (if any!) of the benefits.