Sometimes the PDF itself has to be signed. No conversion from forms. Also, tons of people would rather not have to download the PDF and email it, especially if they are on mobile. There's almost 0 usability advantage to doing that, because Adobe acrobat or whatever other pdf reader that users have and lets them sign stuff is often worse than even a JavaScript implementation. I'd much rather just sign on the browser than send an email back and then... wait or not have an immediate confirmation, or just having to deal with anything else than just pressing next.
I'm sure a lot of people here will disagree but most websites don't target the minority that prefers an email based workflow.
I'm sure a lot of people here will disagree but most websites don't target the minority that prefers an email based workflow.