It punishes fellow nationals for falling in love with non-citizens, while keeping those people out of the country. Or drives the non-xenophobes to live elsewhere rather than be parted. Splits up families along national and income lines, so the entire family is punished. Makes children of those relationships have to grow up with one parent at a distance.
And of course the Tories want to set a price on love and family life, and make it a high price, because they don't give a shit about anyone who isn't rich. Cleverly's own parents would probably have struggled to meet the financial requirement - Tories think nothing of pulling the ladder up after themselves so no one else can benefit from the same rights.
As we can see from Sunak's cabinet, Tories of colour are particularly apt to put the boot in that way, because being as nasty as possible is how you climb the party ranks. Shaft people who would have been like your parents in order to advance your own career. Engender the most hatefully colonial, most racist policies (like the Rwanda deportations, offshoring your quota of refugees in less developed countries, treating those people like unwanted objects in the process) because you have to prove you're not like the other people of colour - the ones without as much wealth or status. There's no end to the bodies they'll climb over to get to the top, and especially bodies that look like their own. That's what a legacy of colonialism demands of the people who cleave to those traditions - not just that you kiss the boot that would have been placed on your own neck, but that you don it yourself and start stamping on others who look like you, look like your parents.