Like anything it's just pros and cons. Sure you save money by doing on-prem or just buying servers and colocating, but you also get all the headaches that come with that.

I used to work at one of the most popular fast food chains. I had one project that was internal to them and one that was customer facing. The internal product, a search engine for documentation ran on-prem while the e-commerce store ran on AWS. Running the former on-prem was just fine.

I'm sure glad we were on AWS for the customer-facing site, though. We'd run ads during the Macy's day parade, college national championship, etc... dear lord I could not imagine wrangling the necessary people to scale that out from an infrastructure perspective. It was very nice just doubling the number on our ASG, failing over to the secondary database, launching another DB instance with double the capacity, and repeating for the second one.

Between those popular ads and DDoS attacks I'd say AWS was a win there, but internal tools don't benefit from the cloud as much. Also not an MBA, but I feel like that's a rule a thumb you can add to the repertoire.