Emails are cheap, quick and asynchronous (contrary to phone), there's a log of the conversation which can be forwarded if need be, and you can attach data to it (document, video etc.).
You can sort your mailbox according to your needs, which gains time and save space compared to, say, hanging folders.
Back in the 90's I tried to attach my VHS tape and Polaroid pictures to email, before sending it over the 2400 baud modem. Didn't work. Also mainly because the other end didn't have any computer or internet.
Should note that email got all that nice features long after it was invented.
Well, email was immediately useful, being like normal mail, only better.
Everyone had an address, almost everyone had a phone, almost nobody had an email address. Not very useful.
How did you send pictures over email? I know what you are thinking, but no, you didn't take digital pictures. If you wanted to send one of your pictures over email, you needed to have an expensive scanner. And if you did, the pixel quality would be terrible. Not very useful.
Technologies like email need things around it to evolve, both technical and social. And the same is true for blockchain and cryptocurrencies.
I'm not claiming that either of them are guaranteed to be successful, but I'm claiming that a lot of arguments against it don't make much sense. Because those same arguments could just as easily be applied to email.
1. I can send a letter to anyone, because anyone has an address. Not everyone has an email address. Plus I can add small physical things, and it's more personal with handwriting and a little perfume ;).
2. If I need quick communication, I just call them.
A lot of arguments that are anti-blockchain and anti-cryptocurrency (based on other tech besides blockchain) can be used in the same way with email.
I can give you pretty convincing arguments why email will fail because we already have traditional snail mail (which can do a lot more), and phone (which is faster and more direct).
Fact is that cryptocurrencies, smart contracts and other blockchain applications live 100% on the internet, which means it's faster, cheaper, simpler, global (= not tied to countries and specific companies)