The best non technical/political reason is that if AWS or Azure goes down or you have an issue with them none of your higher ups or investors are going to ask you, why did you choose AWS. It’s the old “no one ever got fired for buying IBM”.
Besides, you can never go wrong politically by saying I chose the vendor in the upper right corner of Gartner’s Magic Quadrant.
The technical reason is that if I want my hosting service to do more of the “undifferentiated heavy lifting” and provide managed services. I won’t get as much of an offering from Linode/DO. The last reason is that AWS Business Support is excellent. They’ve helped me out with some head scratchers and when I just didn’t want to figure something complex out myself. Their live chat is awesome.
[1] https://www.digitalocean.com/customers/
[2] https://www.linode.com/case-studies