Extended Validation TLS certificates are in theory special TLS certificates that are supposed to give users higher assurances about the website that they're visiting; Certificate Authorities certainly charge more for them (and generally do more verification). There are some fundamental problems with this idea, but there's also a very concrete practical problem, namely that EV certificates are effectively invisible.

Today, the only thing the presence or absence of an EV certificate does is that it changes the UI of the browser URL bar a little bit. Quick, how often do you pay any attention to your browser URL bar when you visit a site or follow a link? I pay so little attention to it that I didn't even notice that my setups of Firefox seem to have stopped showing the EV certificate UI entirely (and not because I turned much of it off in my main Firefox).

(It turns out that the magic thing that does this in Firefox is turning off OCSP revocation checks. I generally have OCSP turned off because it's caused problems for me. It's possible that websites using OCSP stapling will still show the EV UI in Firefox, but I don't have any to check. By the way, if you experiment with this you may need a browser restart to get the OCSP preference setting to really apply.)

This matters because if EV certificates are effectively invisible, it's not at all clear why you should bother going through the hassle of getting them and, more importantly for CAs, why you should pay (extra) for them. If almost no one can even notice if your website uses a fancy EV certificate, having a fancy EV certificate is doing you almost no good.

(This is an especially important question for commercial CAs, since Let's Encrypt is busy eating their business in regular 'Domain Validated' TLS certificates. It certainly appears that the future price of almost any basic DV certificate is going to be $0, which doesn't leave much room for the 'commercial' part of running a commercial CA.)

The current invisibility of EV certificates is not exactly a new issue or news, but I feel like doing my part to make it better known. There's a great deal of superstition that runs around the TLS ecosystem, partly because most people rightfully don't pay much attention to the details, and EV certificates being clearly better is part of that.

(EV certificates involve more validation and more work by the CA, at least right now. You can say that this intrinsically makes them better or you can take a pragmatic view that an improvement that's invisible is in practice nonexistent. I have no strong opinion either way, and I'll admit that if you offered me EV certificates with no extra hassle or cost, sure, I'd take them. Would I willingly pay extra for them or give up our current automation? No.)