Choosing 'secondary' infrastructure providers
While this isn't necessarily needed (you might have every tech solution you need from your primary provider), it's often the case that some things will be a lot better value from other providers. As a result, many websites have one "main" provider and a few secondary providers they rely on for a few services.
With these, there is a lot more choice, as there are lots of providers who have some services but not "every service under one roof".