I'm not sure why this function does not exist yet, since it seems so simple.
The basic idea is to port/forward/link Webflow form data to a CMS collection. So people can send information to the CMS based on a Webflow form. This is greatly beneficial for anyone that makes a platform out of their website.
Currently I'm using a work-around through Typeform & Zapier, which is a hassle, since it uses two other (paid) services. If I'm paying for a CMS website, imo this should be included in the basics.