There really are pros to on prem.
There are cons, don't get me wrong, but to somehow claim that AWS is the end all be all of hosting choices is demonstrably wrong.
For example - You want to develop a financial exchange with a 100 microsecond average response time, peaks of 10Gbit traffic, and 5 9s of uptime. Do you host that on AWS? I wouldn't.
Another example - If I were a medium+ sized company (say 20+ employees), I would want my source control 100% on prem (excluding backup). Internet connections are too flakey, and Github gets DDOSed too often. I could not stake my entire business on github.