Urdu is basically Hindi with a but if Persian sprinkled here and there, it is the regional language of Uttar Pradesh and thus Muslims of UP and Bihar. Its neither native to West Pakistan nor was it the official language.
The only reason we can use it as lingua franca is that its complusory language in our school system and people being bombarded by Hindi movies and songs since our Independence. Muslim leagues was dominated by rich influenctial lords from UP and it was their pipe dream to someday recapture Delhi and Lucknow which is the reason why they wanted to Indianize West Pakistan, so that its easier to rule once they achieve their pipedream.
Our local languages like Punjabi, Sindhi and Balochi are being phased out and lost. For last 1000+ years the official language of West Pakistan region was farsi and our entire history and literature is written in farsi. Majority of Iqbals poetry is in Farsi. Most of our last 2000+ year history was either spent as an independent kingdom from India or as a part of Persian empire. But our history, culture and languages took a 180 degrees Uturn when the British arived at the shores of Karachi in 1842.