It does seem a bit strange for a financial institution the size of PNC (the company has $271 billion in assets) to decide against a platform that has been growing, like Windows Phone. Kantar called it the fastest growing mobile platform on the planet during 2013 (although it did start from a rather low point). There is plenty of momentum with Windows Phone 8, which should only increase with the soon to be released Windows Phone 8.1.
If you are a PNC customer with a Windows Phone flavored handset, you could vote your displeasure by pulling out your account to a more tech savvy bank (Chase seems to come to mind). You could decide to switch mobile phone platforms (although you would be punishing someone not at fault here) or even better, you could call PNC and tell them you want a Windows Phone app. The phone number is 800-762-2035 (option 2). Good luck!