Netlify does the whole static thing better, by being extremely focused on all things static, which makes setting up a static site on netlify way less stressful than on github and amazon, there is also the market knowledge factor, I mean github is known for hosting code repos and S3 is known for hosting files(videos and pictures), netlify meanwhile is known for static pages.
Automatic form handling (by just adding a "netlify" attribute the <form>) is a good example. It's a pain having to set up a whole dynamic infrastructure besides your static site just to record a few form submissions by visitors.
That focus 'thing' is a good advantage all on its own,Netlify is also way easier for non developers to quickly set up their page on than other services, i mean check out just how easy it is ;https://www.netlify.com/blog/2016/09/29/a-step-by-step-guide...
After logging into netlify drag and drop a folder and you have a new site. Or deploy with a git push. Setup netlify cms to push changes to the git repo. Setup a build command to run hugo etc on netlify. Push lamda functions. Setup rewrite rules in a config file. Mirror their setup locally with the new dev feature.
