Emails are just "bigger" entities, in the minds of people than chat messages. They are more massive to use, and for some communications something smaller, simpler is just a better fit.
The "bigness" of an email come from the most usual workflows in mail programs: to respond you have to go through 2-3 clicks first, you usually have to wait some small time for sending them, the contents are usually bigger, there are quotations automatically added, there are signatures, there are more buttons and fields and options in the window - the whole thing is just more massive.
The "bigness" of an email come from the most usual workflows in mail programs: to respond you have to go through 2-3 clicks first, you usually have to wait some small time for sending them, the contents are usually bigger, there are quotations automatically added, there are signatures, there are more buttons and fields and options in the window - the whole thing is just more massive.