"Normal savers" aren't putting a grand a month into savings. People with that sort of sum available are indeed better off putting some into investments or just paying the tax due.
How have we ended up with "normal" people defending the well off?
A bit of history on cash ISAs. They started in 1999 as a reform of the previous Tax Exempt Special Savings Accounts (TESSAs).
Until 2007/08 the upper limit was £3k. Two increases then took the limit up to £5.1k in 2010/11 then for a few years the upper limit was raised annually in line with RPI, which took the limit up to £5940. The 2 big increases were to £15k in 2014/15 and 20k in 2017/18. If the RPI link had been retained the limit would now be somewhere just under £10k, depending on the exact spec of the calculation (which was complicated, each annual increase had to be a multiple of £120 so as not to screw up monthly subscriptions).
I was against the idea when the rumoured limit would've been something like £4k, but actually I think £12k is a fine limit for it.
If the upper limit is reduced to £12k, then it will still be very generous in comparison to years before 2014.
Anyone saving their maximum allowance since 1999 has now been able to invest more than £250k in cash ISAs tax free, more than £200k of which has been since 2014.
The big upper limit since 2014/15 has been a blatant tax break for the rich. In particular it has enabled them to shelter inheritances and the proceeds of capital gains from income tax, by feeding the full £20k allowance into ISAs every year.
It does though because that money is used by banks to fund the mortgage market. It also makes it harder to grow savings for a house deposit. This change will push up mortgage costs and flatten the housing market. A massive dampener on economic growth.
And now a bit of economics. An important effect of the high ISA allowance is that it provides cheap finance to banks and building societies. This helps to keep mortgage interest rates down, but that mainly feeds through into higher house prices not economic growth. The higher house prices then benefit the next round of inheritances and so the vicious circle takes another turn.
The full story of the UK's dysfunctional housing market and how it hinders economic growth would take much longer.