The crescent moon is one of the most beautiful celestial sights created by Allah Subhana Wa Ta'ala.
There are at least five different perspectives:
1. Local - You sight crescent moon, you declare Eid (or beginning of any lunar month), else complete 30 days. This is how it was for many centuries, before means of near-instant communication.
2. National - Moon sighting is done on the national level. If Moon is sighted anywhere in a nation, Eid is declared. If moon is sighted in Gwadar, people of Lahore, Islamabad, Karachi, AJK, all celebrate Eid. This interpretation is based on Nation-state model and is rather recent.
3. Regional - Moon sighting in a region (comprising of more than one country) gets Eid declared. This happens in North America and is followed by some people.
4. Saudi - If moon is sighted in Saudi Arabis, wallha 7abibi, it is 3id. Many people around the world, including Afghanistan just sign off their responsibility to Saudis, who seem to know what they are doing, even when they really do not have a clue like the rest of us.
5. Scientific - Everyone knows how and when moon will be sighted and what parameters are to be put in the calculations. Just print a calendar and be done with it. Turkey (I am told) follows this model.
Masjid Qasim Khan people are following #1 & #4 and are not willing to quit their 2 minutes of fame every year. It makes them important in a very negative way to the rest of the nation.
There is a joke. People name one of their kid "Chand". When asked if they have seen 'Chand', they say that they have seen "Chand" today. Simple.
There is another perspective that I have not included in the list above: The Global perspective. Whenever Moon is supposed to be sighted anywhere, that should be the first day of Lunar calendar the world over. To me this is the simplest and most logical, and also with support from Hadith as far as I know TBH. But that would be too much to ask.
The circus that goes on in Masjid Qasim Khan is getting more and more elaborate as time passes, just because they crave authentication. I've heard that they have begun transporting would-be Moon-sighters to Masjid Qasim Khan and interview them there.
I am all for #2 for now, since we have a valid and institutional mechanism via Rooiat-e-Halal committee. Even if they may be mistaken, they take enough care that I trust them.
My guess is that, if one were to take an empty glass and go around asking people if it was full of water, some people out of millions might actually say that "Yes the glass is full of water". There you have it.