So you only need to bother with a "self-assessment" tax return if you earn over £1000 of casual income.

And then, if you have less than £1000 of expenses related to that income, you don't have to justify the deductions so you just enter the income as a number and you're done.

Charitable contributions are claimed by the charity at the basic taxpayer rate. So when you donate £1 they can claim 20p from the government.

You only need to itemise your charitable contributions (to claim back the difference between the 40p of tax you paid and 20p the charity got) if you are a higher rate taxpayer, which is something like £70k per year gross, so you're well into <5% of people here.

We'd probably see more monkeying around with the standard deduction. I know for me, and presumably a lot of people (especially those without major mortgage interest), the current standard deduction exceeds the benefits to be had by itemization-- and claiming the trivialities like charitable donations or medical expenses.