Benefits of running web app inside docker
Your server itself will not have a big stack installed, like LAMP: all your server needs to know is how to run docker containers.
If you deploy an app with a vulnerability and hackers gain root, they will only have root inside a single docker container, and can’t get at your host system.
If you want, you can run any number of docker containers on a single server by setting up a reverse proxy like nginx or haproxy