While rest of the country was reorganised on linguistic lines in 1950s, why Punjab had to wait till 1966?
Punjab was not reorganized as being a border state govt. wanted status quo. Secondly it was state with mixed population Hindi and Punjabi speaking spread in all districts. Present day Haryana got many Punjabi refugees so Punjab language was spoken from Amristar till Sonipat. Plus the demand for Punjab state was a political demand disguised as a linguistic state demand.
Akali Dal was leading the Punjabi Suba movement without having the full support of non-sikhs and other castes within Sikhs. The movement was too not as strong as in comparison to other states. This made Punjab to wait till 1966.