"Cingular has allowed Apple to launch a device with WLAN and inbuilt services"
At that time, the carriers controlled so much of the cell phone experience. We certainly would have loved to have launched Palm Treo phones with WiFi radios, but our carrier partners wanted the only way to get data in and out of the devices to be through their monetized data plans. They also wanted to control what you did with that data so they could charge for their own email or messaging systems or web portals. The same applied to app stores. Palm OS didn't have a unified app store at that time, just sideloading and some third-party methods, and some carriers had started making their own stores where you could buy apps billed through your cell phone bill. They hated the idea of a platform owning that, and I expect that was part of the reason Apple originally released it with no app store. They needed the phone to be a massive hit in order to gain the power to also bypass that wall that the cell companies put up.
Palm did benefit from the iPhone launch -- it had us uplevel our efforts away from the post-Palm OS phones that we were in the middle of developing that were aimed at the RIM market and instead try something radical with webOS, and when the Pre launched, it actually had WiFi on board, although the Sprint-exclusive Pixi phone lacked WiFi due to carrier request. There was some momentum there for a while, but then HP bought us, hit its own set of brick walls with carriers, and ditched the hardware business shortly after Apple started launching on other carriers.