I'm reading over the WFS 1.1.0 spec (0GC 04-094) and see in section 6.3.1:
HTTP supports two request methods: GET and POST. One or both of these methods may be defined for a particular web feature service and offered by a service instance. The use of the Online Resource URL differs in each case.
HTTP supports just two request methods? I could understand an oversight like this in a spec from 2000, when RFC 2616 was still just one year old, but WFS 1.1.0 was approved in May of 2005. Browser forms support GET and POST only, but that's not a limitation of HTTP/1.1, and the XMLHTTPRequest implementations in almost all browsers do support the full range of HTTP verbs.
On the other hand: the WMS 1.0 spec (00-028), to the credit of its authors, doesn't make the same mistake and even references RFC 2616. Somewhere after WMS 1.0, the OGC lost the trail to REST.