There are a lot of good points in this thread, but I just want to mention that there is a very good reason to use email for purchases like this, as well as really any business matter.

Email creates a record of what was said.

And I say this not as a "gotcha" type of thing or as something to be used in a lawsuit (which is hopefully never necessary). But simply, it will help you remember all of the details.

How many times have you discussed something on the phone and later tried to remember some detail about it? Well, with email you can go back and look.

Same thing would apply to texts/messaging, etc, but it's simply easier for all to convey larger amounts of info in email than texts.

In my job I always want to hash things out via email rather than a conference call. Yes, it's not as fast or efficient. But there's a really good reason they people (and much of the business world) still use email.