Why Publish is sending every time all files to the server?

Question

I'm Publish to a server my ASP.NET MVC application, under Visual Studio Community. But once I do Publish->FTP, it always send to me all files/bin every time.

It takes 2-3 minutes every time. Can't just deploy the "changed" edits?

Or is it necessary to deploy all every time?

Note: Delete existing files is set to false, of course.