Zoom has clearly focused on UX above all else. This explains both their popularity and the security issues that have recently been uncovered.

First thing that comes to my mind is: a friendly URL in a email body that doesn't get clipped or mangled in such away that it can't be easily opened.

Ease of use, probably.

Now every private room is by default secured with a password, I think.

> Was there any rational for them doing this?

Conference ids are numbers for easier dial-in?