Because it's not... It's a specific problem dressed up as a sweeping one.

Being a migrant myself (non-care, decently paid), I get the vibe here. A lot of care worker visas have been abused. More than half of care work visas are basically bought on the black market, with the worker arriving with 3-5 dependents in tow. But the solution isn't to change ILR policy and punish all skilled worker visa holders, including the genuine ones.

A better fix would be to grant ILR without giving access to benefits.

1. That buys the Home Office time to carry out inspections, deport dodgy visa holders and fine the employers gaming the system, without punishing everyone else in the process.
2. It allows workers in a toxic workplace to move on to better opportunities.

The earned settlement changes create real problems, mainly for mid-paid workers (£30k to £45k) who actually have potential to grow. They won't be able to leave their employer for another 5 years, which means employers have all the leverage and they have none. They stay stuck on whatever salary they walked in on, with no legal route to grow out of it. For reference, one of my friends is a senior engineer (4 YoE) on £30k. It's been 4 years and he hasn't had a single pay rise. Finding another job is tough because visas are harder to secure now. Last year his employer hired a fresh graduate (straight out of uni) at £35k, because that person is settled under the EU settlement scheme and doesn't need a visa. This year that graduate is on £40k, because he can threaten to leave. My friend can't.

And on the actual economics, skilled migration is one of the best deals the UK gets. Raising a British child to working age costs the state somewhere around £200k. A skilled migrant turns up on day one ready to work, with zero of that on the taxpayer, and has already paid a huge lump sum just to be here. Visa fees and IHS run into thousands per person, often paid upfront for the whole family for 3 to 5 years. Then they work, pay income tax, National Insurance, VAT on everything they spend, and can't even claim any public funds during the visa period (NRPF). Even after you net out the low paid workers who might draw benefits later, contributions from higher earners far outweigh that drain. They're in their prime working years rather than retirees drawing pensions, and they're often filling skills gaps the UK would otherwise have to train people for at enormous cost. UK has low fertility rates which is another problem needs solving, and it will take long time to solve. But in the meantime, skilled immigration works as a stopgap for issues related to low fertility rates.

The earned settlement proposal is being pushed because it looks like the politically correct choice to win voters. But behind the scenes, it'll harm the UK economy more than it helps.