The Tories who were in power pushed it based on right wing conspiracy theories about immigrants because vulnerable populations least likely to have government documentation vote overwhelmingly labour.

It didn't really work though because old people also often let their passport and driving license lapse, department of work and pensions also already uses heavy handed documentation requirements as a way of fucking over people with mental health issues, criminal records, poverty etc who are less likely to have ID so the amount of people with ID in those groups is uncharacteristically high.

So yeah it's a bit of a nothing really, reduces voters on all sides but mostly the left and doesn't really seem to do much else.