Axix of power
Delhi is the centre of power in most cases throughout which whole india was ruled. To occupy india; delhi must have to be vanquished. Panipath is the nearest location where a battle inevitably happens before defeating the axial power in Delhi.
Most invaders come from north west region. For them; panipath positions in a suitable route in their war map throughout which it becomes possible to rule india defeating the power in delhi.
Generally; a war is fought in a secluded place. Panipath comparatively bore less population. Besides this; its plain and slopy hilly area gave a chance to fighters to use tactical war strategy like ambush; accidental attack etc.
The existence of river yamuna; Ganga provided a war route like fighting ; escaping etc. Those who have an ambition to rule india can use them to extend their rule after occupying Delhi but for which battle has to be fought undoubtedly from panipath.
In which krishna godavari was an area of disparity in south for its rich fertile land; Uttar Pradesh; Bihar nearby ganga were place of resources that escaped in the mind of invaders. But for this coming through the route of delhi before defeating her from a safe battleground like panipath is inevitable.
The north west invaders landed in punjab crossing khyber pass with immense dream of conquering a territory. Punjab provided them stable settlement through agricultural resources. But there was not any centralized power in western india except Peshawar. The pathan and other tribal people were not a supplement with whom they can dream of conquering india. Moreover; a battle from punjab would invite huge loss of agricultural revenue and civilian loss which the invaders did not want to loss for the sake of their last resort of gain. Deviation from punjab would put their eyes in delhi and suffuce it to say who can provide a cool battlefield than panipath to conquer Delhi.
The grand trunk road runs nearby the route of panipath. It facilitated carrying of weapons ; armies etc.
Attacking delhi from northern route crossing unfathomable himalaya and so many territories was quite unviable for the invaders compelling them to think another route where panipath comes with golden opportunity for them.
Panipath in haryana was a buffer zone above all. It provided safe foodstock from punjab. Its geographical location; communication strategy provided an essential battlefield. Even they were defeated then also they would have gained enough from revenue of Punjab which made the invaders in a safe place.