The fact that the entire "chances of" rationale fundamentally misstates the problem. How many chances you have of obtaining a certain outcome are largely irrelevant apart from correctly evaluating the events required for that outcome to take place.
In a very real sense, the whole line of reasoning is predicated on "the gambler's fallacy." ....hence my reference to Michael Crichton and his famous speech on the Drake Equation before SETI.
Sure, but Drake’s equation is just a Fermi estimate - a reasonable guess about a matter we don’t have nearly enough data about. There’s no doubt the press sensationalizes such mind-exercises and the speculations some scientists attach to them, but the fact is that we do know that intelligent life is allowed by the physics of this universe. Speculation about how often it occurs is certainly more legitimate than speculation about how common water flowing uphill on other worlds might be.