I believe everyone should have a personal allowance no matter what.
Yes, I can't believe that this is up for debate - and I say that as a disabled person who is unable to work enough hours to even earn 5 figures.
If somebody earns over £100K, they're already paying a load more tax than somebody on £20K, so the basic system has worked well, without tugging at the roots to take even more from them as a non-progressive punishment for earning well. Why should they get the TFA? Why shouldn't they?
It's like with the winter fuel allowance, and you get people arguing that mega rich celebrities like Mick Jagger also qualified... so what? He earns an enormous amount of money - which means that he pays an enormous amount of tax, as he should. The more you earn, the less material any free allowance that means something significant to ordinary people actually is to you or to the country in terms of your overall contribution.
Seeking to take basic universal entitlements from people is a slippery slope. What would happen if we said that people earning over a certain amount would no longer be allowed to use the NHS, or to send their children to state schools, on the grounds that 'they earn enough not to need it'? Yes, mega rich people likely choose to go private for these instead; but they shouldn't have the entitlement forcibly removed from them... especially as they are amongst the net contributors paying the lion's share for them in the first place.
Cliff edges are so very obviously a poorly-thought-out, ineffectual, unfair policy that are designed to inhibit growth and to hurt the economy. It's the same with small businesses and VAT registration: even all the honest ones that don't massage their figures and ask for cash to avoid putting extra work through the books are thus strongly incentivised to turn away work and limit their turnover, and thus limit the amount of tax that they pay. Nobody in their right mind is going to want to suddenly have to charge 20% more for every job they do, only to not see a penny of it themselves and to have a lot of ongoing extra admin to do on behalf of the government.