Very interesting question. As an Italian (specifying this because it probably changes what and when things happened), I remember this transition started to happen in 2010 mainly because of Facebook.

It’s difficult to say why we decided to go with real names on that platform when there were already other similar ones (netlog was super popular here), where most people were mostly semi-anonimous (real pictures, fake names). I totally agree with another comment which said we started to realize internet was not that dangerous or bad, which probably made this happen, combined with the fact that Facebook explicitly asks for your real name.
Back then, I feel there was also much less attention to privacy on the internet (or maybe it’s just because I was a teenager), and it felt super exciting to engage with every new platform or website.

Debian ships with vanilla Gnome. This means that what you’re seeing is exactly what you’re expected to see. If you want the typical “ubuntu-like” (or mac-os like) dock, you should install the dash-to-dock extension