Most companies severely understaff ops, infra, and security. Your talking points might be good but, in practice, won’t apply in many cases because of the intractability of that management mindset. Even when they should know better.
I’ve worked at tech companies with hundreds of developers and single digit ops staff. Those people will struggle to build and maintain mature infra. By going cloud, you get access to mature infra just by including it in build scripts. Devops is an effective way to move infra back to project teams and cut out infra orgs (this isn’t great but I see it happen everywhere). Companies will pay cloud bills but not staffing salaries.
It's the exact same reason why most companies don't just run their own power stations, and instead buy it from a power company.
Computation has become a utility these days - this includes the fat ISP lines and connectivity etc, not just the CPU and harddrives. These things have economies of scale that smaller companies cannot truly reach, and will pay a huge fixed cost if they want state of the art management, monitoring and redundancy. So unless you are a massive consumer, just like power stations, you really don't need nor want to build your own.
I’ve worked at tech companies with hundreds of developers and single digit ops staff. Those people will struggle to build and maintain mature infra. By going cloud, you get access to mature infra just by including it in build scripts. Devops is an effective way to move infra back to project teams and cut out infra orgs (this isn’t great but I see it happen everywhere). Companies will pay cloud bills but not staffing salaries.