Joelsnan, because the rules changed. None of this group are illegal so it's not anything about them "keeping quiet". From an immigration lawyer:
"The Windrush Generation refers to the Commonwealth citizens who came to the UK between 1948 and 1971. These Commonwealth citizens were encouraged to come to the UK to fill the countries labour shortages – such as bus drivers and nurses. Yet, when the Immigration Act 1971 (“the 1971 Act”) came into force, Commonwealth citizens lost their automatic right to remain in the UK and they faced the same restrictions as migrants from elsewhere. For those who were already living in the UK, they were granted Indefinite Leave to Remain and for decades since then, many of the Windrush Generation considered themselves as British. However, at the time these Commonwealth citizens, mainly from the Caribbean, were not issued with the requisite documentation which demonstrates their right to be in the UK.
When Theresa May was Home Secretary in 2012, she introduced a Hostile Environment Policy in order to reduce the UK’s net migration figure to less than 100,000 and crack down on illegal immigration. As a result, many of the Windrush Generation have fallen victim to the Home Office’s robust and objective policies and some have recently lost their jobs, access to NHS services, or even been detained in immigration removal centres. Theresa May’s changes to the UK’s immigration laws and environment has meant that the Windrush Generation have had to prove that they have been living in the UK for decades by providing 4 sources of documents such as bank statements and payslips for every year they have been in the country. This is despite these individuals having paid tax in the UK for decades and frankly an impossible and ridiculous task."