Care to elaborate?

Maybe because there are many other currencies besides bitcoin, what about ripple, litecoin, etc? Would they alter the standart every time to add one of them?

If those currencies gain traction comparable to Bitcoin, why not? The standard is being changed every day anyway.

I believe they can use "web+litecoin" in the meanwhile. When they'll get enough traction, they may get their designated "top-level" scheme.

Same as with MIME types: application/vnd.org.example.foobar for anyone, application/foobar when you're famous.