Do you know what happened to the Kingdom of Amarkot? A Hindu majority region opted for Pakistan. Pakistan which was created in the name of Islam for Muslims.
Footprints: Once upon a time in Umerkot
Pakistan was only for Muslims & India was for the rest, that included everyone who was not a Muslim & also for those Muslims who did not want to be a part of a fundamentalist Islamic country.
Bollywood Playback singer - Mohd Rafi’s family returned back from Pakistan as they understood that a fundamentalist Pakistan would discourage anything that was against its interpretation of Islam.
In the 1970’s, main backers of Pakistan, the Ahmediyya Muslims too were declared as non-Muslims. So imagine the condition of non-Muslims.
In the 1971, Bangla speaking East Pakistan separated from West Pakistan, as West Pakistan considered a non-Urdu speaking Bengalis, lesser Muslims.
So, the leaders of the Sikh community clearly understood that their future lies in a India of composite culture than in a Islamic Pakistan.
Just as Jainism & Buddhism are results of intellectual reform movement in Hinduism in ancient era, similarly Sikhism is a result of reform & Bhakti movement in medieval era. Culturally Sikhism is an off-shoot of Hinduism.
Islam has nothing much in common with Sikhism. Moreover many Sikh Gurus lost their life in the hands of Muslim invaders, who are represented by Pakistan.
Sorry for being politically incorrect, but as the saying goes, one Muslim guy can stay with 10 Hindus / Sikhs, but one Hindu/Sikh can not live with 10 Muslims.
Edit 1: As per the law in Pakistan -
Only a Muslim can be appointed as President.Only a Muslim can be appointed as Army Chief (service Chief), this was one of the reasons for declaring Ahmediyyas, as non-Muslims, to disqualify high ranking Ahmeddiya Muslim Military officers from becoming Service Chiefs. The other reason was Saudi pressure.Only a Muslim can be appointed as District Collector / DM / DC.
In Pakistani Punjab, Muslim Punjabis are a majority, whereas in India, Sikh Punjabis outnumber Hindu Punjabis. Therefore if Sikhs had opted for Pakistan, they would have remained a minority in Pakistani Punjab, whereas in Indian Punjab, they are the majority.
Edit 2: Sikhism & Punjabi in Gurumukhi are inseparable. Punjabi in Gurumukhi is the language of Guru Granth Sahib. In Indian Punjab, Punjabi in Gurumukhi is the official language of Punjab. Punjabi is the first language of education. Punjabi in Gurumukhi is a recognised language of India.
In Pakistani Punjab - Teaching of Punjabi is not encouraged in school or college. It is against the law to speak Punjabi inside Punjab (Pak) state assembly. Whatever little Punjabi survives in Pakistan is as mother tongue (mother speaking to her children). Rest is due to unofficial promotion of Punjabi in shahmukhi (persian script).
Perhaps after a century, Punjabi will survive as a language only in India.
Edit 3: Footprints: Once upon a time in Umerkot
Edit4: For those with doubts -
Who is a Hindu? -
People living on the banks of river Indus (Sindu) & East of river Indus, are collectively called Hindustani, Hindu or Hindi.These people follow a culture, faith, tradition, rituals, costumes, festivals etc which were passed on to them by preceeding generation from the time, when their ancestors were gatherers & hunters. People worshipped snakes, spirits, ghosts, & lord of ghost (Bhootnath).Later agriculture lead to stable village life. People worshipped animal, plants, trees & lord of animal & tree (Pashupati). People worshipped special stones (Vaishnodevi etc). Black magicians were the priest & very popular.Much later, due to excess of food grains, when everyone was not required to be engaged in agriculture or allied trade, some people took part in other work, such as art, dance, teaching etc.Much later, basic literary practices led to higher education, free thinking & knowledge. People worshipped the shedding of ignorance & gaining of wisdom. People worshipped Ganesha.Much later, some of those educated knowledgable guys, questioned the beliefs in God / supertitions / rituals. Much later, this challenge & questioning led to Jainism & Vedas.Much later Vedas were challenged, which led to Srimad Bhagvatgita & later Buddhism.Much later, this led to stories & dance dramas, some inspired by real events & rest based on fiction. Much later, this led to mythological characters being worshipped as deities. People worshipped Rama & Krishna.Much later, love towards certain deities & god, led to Bhakti. During bhakti movement, Sikhism emerged, merging Hinduism with Sufism.
Those who do not consider the primitive / ancient culture, history & rituals of Hindustan as their own, are Non-Hindus. These non-believers include, but not limited to, the present generations of Jains, Buddhist, Muslims, Jews, Christians, Parsis & Sikhs.