Travel between India and Pakistan requires a visa that is issued for named cities, requires police reporting on arrival in most categories, and is refused far more often than granted.
For Punjabis this means that a journey of fifty kilometres from Amritsar to Lahore is administratively harder than a journey to Canada, and takes longer to arrange.
Pilgrimage under the 1974 protocol is the main exception: four jathas a year, with agreed numbers, to named shrines. Demand consistently exceeds the allocation by a wide margin.
The Kartarpur corridor, opened in 2019, is the only visa-free arrangement and it covers one shrine, one day, and a fee.
The effect on knowledge is direct. Almost no Indian Punjabi historian has worked in the Lahore archives and almost no Pakistani Punjabi historian has worked in the Patiala ones, which is why there is no history of Punjab written from both sides of its own record.
That is a solvable problem that neither state has any interest in solving.
There is no tourist visa between the two countries. The categories are visits to relatives, business, pilgrimage and official travel, so a Punjabi who simply wants to walk around Lahore has no category to apply under.
The religious pilgrimage protocol of 1974 provides for parties to visit named shrines on named occasions, and those parties are how most people who cross do it.
A family divided in 1947 that wanted to meet has to do it in a third country or not at all. The two halves are fifty kilometres apart and the trip is effectively impossible.