Wechat is what's doing this is China, and it's working fairly well for them. It's obviously impossible to do the same in the West (companies won't be trusted by people in Europe, nation-level apps won't be trusted in US) but it's not impossible to replace email. Note: mobile is gigantic compared to desktop in China, so this might also be a reason.
I still believe email will outlast all the current solutions though, but the crushing presence of a few big providers is not doing any good for the protocol.
While WeChat is somewhat more advanced then its rivals, the reason it works is because Chinese businesses are less 'sophisticated' than western ones and much more human based. WeChat is to a large extent a phone call replacement, which is especially useful in a country of multiple languages and dialects but a common written one. Western messaging services are mainly replacing things like text messages and other instant messengers not e-mail. (e-mail is probably still the de facto most insecure protocol on the internet and should be replaced).
Replace? That's a strong word but it has more or less deprecated paper mail. Everything from insurance cards to my recent W2s are delivered electronically via e-mail now. I recently bought a car and all the paperwork was completed online. The bank uses electronic signatures for everything. The amount of first class mail delivered by USPS has halved over the last decade. Is paper mail dead? No. Is it on it's deathbed? Probably.
So 20 years of internet, the rise of mobile and hi-speed connectivity, the multiplication of communications means including emails, chats, text and social network and the paper mail is still here.
I still receive all my most important communications through the mail box, including anything related to administration, voting, my landlord, invitations to major life events, bank details, etc.
Now if you hope to kill email, you gonna have to remember that.
Well, I think some of this can attributed to personal preference. Each of the use cases you described can be accomplished via e-mail or other electronic communications. Other than a wedding invite or two every year, I receive no other personal mail. This didn't require any special technical skills, many organizations actually encourage you to setup paperless accounting when you sign up for a new account.
I still believe email will outlast all the current solutions though, but the crushing presence of a few big providers is not doing any good for the protocol.