Some random points, hard to say in detail:

Browsers tend to not automatically open new tabs though, but only if you explicitly do something to cause it.

Maybe many people do not use multiple tabs within one site/app, and that doesn't translate (There's probably some research out there on how people use browsers in practice)

Your app might look and feel too different from a browser or other tabbed environment. Does it clearly communicate where a new tab is opened, that you can't go back on it, ...?