I can understand the annoyance for there being so many verbs, but at the very least, there must be two: One that is guaranteed to be idempotent, and one that isn't.
Someone I know was trying to make a message board that was compatible with every browser. EVERY browser. Including Mosaic and Netscape 1.0. Which meant that everything was done using GET requests, including posting messages.
He changed his tune when some spidering engine found his site and issued tons of GET requests that ended up flooding the board with comments and posts that looked like web search queries.
OTOH, sometimes the best teacher is experience.
Instead there's a workaround for a serious problem, and any client (browser being by no means the only client) which doesn't respect the convention can emit identical POSTs, with no way of knowing if that was intended.
We saw this when MS would regularly ignore HTML standards.