Why hasn't AWS bandwidth egress cost come down?

AWS egress is cheap, just not for you.

If you're a small developer you get to pay for those fat AWS profit margins. If you're a larger company doing VERY LARGE amounts of egress (where it's potentially economical for you to lease and manage your own fiber lines) you'd be shocked at just how flexible the AWS sales team can be.

Source: participated in egress pricing negotiations with AWS for a large company and saw the real numbers.

I think they would if either Azure or GCP lowered theirs. The bandwidth pricing for all 3 is very similar. I think neither of the 3 wants to reduce the margins on this, since it might significantly make cloud a much lower profit business, and that would make winning in it pointless. It's better to make good money being 3rd than to be first in a commodity market.

Because AWS wants you to switch to custom pricing with Cloudfront, not serve things out to Cloudflare.