We had cases when a prospect said we must use AWS (because that's what they use, and are comfortable with how our data bridges would work/integrate), and when a prospect said we must not use AWS (because they are in retail and want to avoid feeding the 1,000-pound gorilla that's mauling them).

I don't want to imply this is common - it's not. Such cases come from the "arbitrary enterprise rules" side rather than the "SaaS/tech" side.