On call is a dysfunctional company culture attacking its own workforce in a battle of attrition. Its the equivalent of rheumatic fever to a company process. If you need it, your reliability engineering is failing and the process that should mend it, is instead busy fixing symptoms.

Such a company is already dieing and will do once the team "on call" is used up, burned out and gone.It will be replaced in the market by something more vital, still capable to value its workforce.