It is often noted during the discussion of the HTTP PUT and DELETE methods that HTML forms and XForms do not support PUT and DELETE.

There is a valid argument for allowing the full suite of HTTP/WebDAV methods to be used by forms developers for a model of resource interaction where a user can retrieve, store, and delete uniquely identified resources via a "forms" representation.

A confusion comes in to play in that forms are also (more commonly today) used for a different model of interaction: "interactive web applications".

MarkBaker writes on the WwwTag mailing list, in [WWW]HTTP Methods,

In a non-browser client, such as an Atom reader, the client itself is the "interactive application", capable of validation, progression, and otherwise handling the interface between the user and identified resources stored on the web, in most any representation.