I have an XD-45 Tactical that I use as my beside gun. It has no thumb safety, and frankly doesn't need it. For the vast majority of civilian shooters, the thumb safety certainly isn't really necessary.
That said, if I were considering this pistol to arm my police department, I absolutely would insist on the thumb safety. It's happened more than once that an officer's life has been saved when a suspect got hold of his gun, but couldn't immediately figure out how to make it fire. In a gun grab, the thumb safety can give you a precious extra few seconds to regain control of your weapon, or better still, deploy a backup. As to the complaint that a thumb safety may trip the shooter himself up under stress... that complaint holds absolutely no weight, as far as I am concerned. A properly designed thumb safety describes the same arc of motion as the shooting hand thumb; it simply wipes off easily and naturally during the draw stroke, and this is certainly no more difficult a motion to make under stress than undoing a thumb break strap, or pushing the release button on a retention holster. If there are shooters who failed to disengage the thumb safety under stress it is because they foolishly neglected their weapons training, and didn't familiarize themselves sufficiently with their pistol and its method of operation. The 1911, after all, has been carried as a police sidearm from it earliest days, and generations of officers (and others) who carried it cocked and locked, and used it in gunfights, have proven beyond any doubt that for a properly trained shooter, a thumb safety of that type is absolutely no impediment to a swiftly delivered first shot from the holster. Indeed, Jeff Cooper built his fame partly upon proving that for a properly trained shooter there actually was no faster gun to a first shot from the holster than a cocked and locked single action.
I gather that Springfield added the thumb safety partly to appeal to shooters who wanted one (the aftermarket thumb safeties sold for the Glock prove there is a market for such a device), and partly to make the gun a contender in any future U.S. military pistol selection, since the U.S. military insists any handgun it will consider as a possible future replacement for the M9 absolutely must have a thumb safety. For military usage, I really would consider the thumb safety a superfluity on the XD-45, but if that is what the U.S. armed forces want, the manufacturers have to accommodate them if they want to be considered.