Not all brokerages will always have their own internal supply of a particular stock...especially stocks with low liquidity, which means stocks that are infrequently traded.
They won't. That is why we have Market Makers. CRGP was on the Grey Market for years, and so had no MMs, because it lacked a new Form 211. Inexplicably, OTC Markets REMOVED it from the Grey Market (which is an SEC thing) and elevated it to Pink No Info. Simultaneously, it allowed it to be quote on an unsolicited basis.