At least in my experience, managers (engineering managers, sorry for not being more explicit. I didn’t mean product managers or similar) have a good number of years of experience as software engineers before turning into managers. They are not clueless about the products we built and maintain. So, even if junior engineers are on-call, why on earth an engineer manager with over 10 years of coding experience cannot be on call as well? In my experience, the answer is: because being oncall is shit, and upper management cannot force middle level managers to be on call.

Sounds reasonable but misses the mark, sorry. Once you become a manager you rapidly lose hands on skills. The big picture never goes away, but the details go pretty quick. If you don’t use, you do lose it.