It would be foolish for a business to enter into BTC-denominated contracts because that would expose them to a huge foreign exchange risk in return for nothing.
If you don't possess the BTC on the day you signed the contract then you basically created an option with a zero dollar strike price. You aren't truly using the currency the way helloworld1 and others imply.
They do so because it gets the job done.
You'll get really tired from all of these gymnastics trying to convince everyone already using cryptocurrency that nobody's using cryptocurrency.