It's exactly the other way around for me. Any text that isn't directly in the email will either get ignored or I won't reply in as much detail as I would have. It's much more difficult to quote selectively from attached files so I don't do it.

And printing is about the most horrible thing ever invented. I only do it under threat of financial loss (return labels, letters to tax authorities). There's nothing as broken as printing. It never works flawlessly and I can't focus on printed text anyway.

Printed text has no search, no copy and paste, no changing font sizes or brightness, no hands free reading, no place to put paper without it getting fatty or full of coffee stains.

So I guess the conclusion has to be that there is no general right or wrong when it comes to the length of text in email. I depends on who you are sending it to. I pity whoever has to correspond with the both of us :-)