EV and normal certificate have a very different goal in mind. On the one hand, certificates are for everyone. Everyone can and should get a certificate for their domain the only requirement is to own the domain.
EV on the other hand is a real proof of identity, not just the domain but that this domain is indeed the domain of this company that your are indeed a representative of this company, etc. It doesn't verify just the domain ownership but the real physical identity. That's a higher level of identity verification and thus a higher level of trust and it obviously can't be automated. And even if it could it shouldn't, the human verification is exactly what makes it more valuable.
The point of let's encrypt is that it is easy to get, so that every single website on the internet get https.
The point of EV is that it is hard to get. So that phishing gets harder. You probably can get a certificate for a domain trying to imitate a well known domain but you can't get an EV certificate for such a domain, because no human would allow that.
So making EV certificate free and automated by bots is completely missing the point of EV and it would lower the trust we get in all other EV protected domains. There is no point in having EV, if everyone can get one for free automatically. The extra price and verification is what make EV... EV.