I use Heroku because I can link it to a GitHub repository and simply click 'Deploy' in the Heroku dashboard. When I'm working on little hobby projects it's nice to be able to get things into production as quickly as possible - and all for free! Setting up domains is also really easy. Heroku is perfect for prototyping and getting something on the internet for people to see but I'm not sure how well it'd do for massive projects. I'd stick to docker/kubernetes + AWS if you need to scale.