The longer the balloon stayed aloft above the US, the more info was gained from a DOD perspective. Shooting it down while over the country made no sense and was most likely never the plan. Tracking it did as there was a chance it would have exploded on its own anyway and easily found given the interest in it.
These probing operations happen all the time and the Chinese certainly learned something about our capacity to identify this type of object. We learned a great deal as well starting with when it was discovered, at what altitude, etc. etc.
It would be interesting to know when it was identified over the pacific and by what means.