Debian is a large, complex operating system, and a huge open source project. It’s thirty years old now. To many people, some of its aspects are weird. Most such things have a good reason, but it can be hard to find out what it is. This is an attempt to answer some such questions, without being a detailed history of the project.
Please define what you mean by vanilla.
For people who want a desktop, I either tell them to install it themselves or go for LMDE if they don’t really care as much. But I wouldn’t voluntarily use Debian, I don’t like distributions running Systemd