Play store My App section When i open the play store -> My apps section from my PC, i see a list of all the apps i ever used. This list is uneditable. 
When i check the same in the play store android app, i see the same list but this time i can delete entries.

Questions:

-Why this list shows all the apps i ever used? I would expect to show all the apps i currently have installed on my phone.

-For what purpose this list exists? What happens when i delete entries manually?
You might want to see apps you have installed previously but since uninstalled in order to find an app that you but want to recommend to a friend. You might uninstall an app by accident and want to find it again easily.

Google Play needs to keep track of this information anyway, for two reasons:-


You can only review an app you've installed;
Even after uninstalling a paid app, it remains available to you, and you can reinstall it again without paying.


Deleting an entry only hides it from the list (on all your devices and the web interface), and has no other effect.