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".
One of my issues with forms and PUT/DELETE, is that unlike GET and POST, neither of those methods progress the hypermedia application(*). Another way of saying that, I think, is that POST can be parameterized (and GET too, though not necessarily so) such that the state to which the application transitions is a function of some input data separate from the set of representations available to the agent. But with PUT and DELETE, at any place in the application, an agent has the option of PUTting or DELETEing a resource independent of the particular application that it's participating in (i.e. unparameterized).
I believe this explains why PUT and DELETE support can be (and typically is) handled "outside the browser window" (i.e. File->Delete, File->Save), but parameterized-GET and DELETE need "form buttons" inside the window.
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.