Why burn fuel at departure airport instead of flying to destination before emergency landing due to deflated tire?
I have no idea what a deflated tire indication is on a 737, but perhaps the news media got something wrong in their reporting. (Nah... that never happens, does it???)

That said, the cardinal rule of landing gear problems is to leave a good configuration alone, so don't retract a gear with a possible problem, since it might not come back down again.

With the landing gear extended, your fuel burn per mile is far greater than with the gear up, so "enough fuel to get to XYZ" (based on normal gear-up cruise) isn't nearly enough to get there with the wheels down.

Any time an airliner takes off from a field they couldn't return to (most often, this comes up because the weather isn't good enough for a published approach back in), they have a "takeoff alternate" that they could get in to within a prescribed distance -- typically an hour's flying time.