RE: I wonder how many people care this function?
I believe the problem of getting mysterious extra lines in your CF7 forms is fairly common. It is certainly mentioned at regularly intervals in posts in this forum.
I've personally found it is very common to get CF7 forms not displaying as I want due to extra lines being added. I can usually work around it with CSS, but not always, and it would sure be appreciated if I didn't have to.
Also while users can disable the ‘autop’ filter by setting WPCF7_AUTOP as false in their wpconfig, that's an area that many CF7 users are reluctant to go.
Also it's propably more of any issue when forms are used in Widgets (where I expect Chudz is using his CF7 form) where WP does give users the option to "Automatically add paragraphs" in all Text widgets, with the default being ‘autop’ disabled.