Sometimes it isn't the users fault,
I recently did a customer satisfaction survey for a Premier Inn which ended with a link to write a TA review for the (wrong) hotel.
In the TA review form which was embedded in a frame on the web page the newline key just did not work forcing the review to be typed as a single run-on paragraph! When I realized the review would be unreadable I deleted the review and will have to resubmit by the normal route
Sometimes you get web input forms that appear to allow you to format your input with paragraph breaks and then strip out all formatting when you submit the form. I see this quite often on 'email customer support' forms which send you a copy of the submission - I pity the customer reps who have to unpick the resultant mess.
On the Other hand we have the TA forums which insert a blank line after each paragraph whether you want it or not. Sometimes it would be nice to be able to type a compact list without extra spacing ans especially when pasting text from elsewhere,