Document Tabs is a well-known paradigm, thanks to browsers.
Since many of us spend a lot of time with browsers, we expect the same functionality form tabs’ headers in Illustrator.

One of them is a middle-click to close a tab (https://illustrator.uservoice.com/forums/333657-illustrator-desktop-feature-requests/suggestions/38150188-add-middle-click-to-close-document), another is remember opened tabs on relaunch (https://illustrator.uservoice.com/forums/333657-illustrator-desktop-feature-requests/suggestions/44819065-launch-illustrator-with-the-same-opened-documents).
There are others.

But the most prominent one is the Plus button to the right (in LTR world) of the last tab, which creates a new document.

Sure, one can hit Cmd/Ctrl+Alt+N, or go File > New, but sometimes we are lazy, and the other hand is used to hold the head or a cup of tea.
Accessibility and consistency are great.

BTW, Corel Draw already has it.

And if you want to make a step further — do the same with a double-click in that area as well. It’s like a super long button (when you have little tabs opened).