If all the recent supply chain hacks didnt convince you then maybe the aws outage will - own the stack, control your externalities (maybe your primary load is self hosted or multicould but how many of 3rd party things you have in your supply chain and stack that will fall apart?)
Can you deploy when docker registry is down? Or if github has an outage? Does your team communication still work or is everything dead silent because you didnt know you had another 3rd party dependency?
Try having a major outage and no ability to coordinate people. Do you even have the contacts for everyone needed that are not their work email and slack?
The rabbit hole is endless and the horror stories are terrifying.