In a vacuum, technology does not need people on-call. The problem is when you're iterating on technology (E.g. SaaS). Shipping things has the highest risk of b

In a vacuum, technology does not need people on-call. The problem is when you're iterating on technology (E.g. SaaS). Shipping things has the highest risk of breaking something. I worked with an SRE team responsible for managing incidents for a few months, they told me that ~80% of incidents are caused by bad code being shipped, and I saw that happen as well. Modern software applications are complex and interconnected. It's pretty easy to unintentionally break something in a different part of the application, or ship subtly bad code because you aren't intimately familiar with that part of the codebase.