If accounting for every expense was cost effective, we'd already be doing that.
It isn't. It would be an absolute nightmare to run. We have that system for Access to Work because its a much more limited scope of things to pay out for, we also have the personal budget scheme for PA's, where you are assessed for how many hours per week of PA time you need - and you only get that sum of money, its up to you to hire your PA and pay them as an employee - so that is pretty closely managed to.
But to run a system where for 1 person, food and clothing costs would be an acceptable expense but for the next person, iPads and physio would be and clothes and food would not... is a logistical impossibility. You'd spend billions trying to run that, mistakes would be made all over the place, then people would be asked to repay money they spent on something they thought they were allowed and then were told they weren't... whilst others were going without things they need but think wouldn't qualify...
The current system of 'heres what we think the extra cost of being disabled is, its up to you what you do with it but you aren't getting any more if you spend it on cake' is the simplest and most cost effective way of doing it.
Yes, that does open it up to both parental and spousal abuse. But that is a seperate matter with different channels for dealing with it.
Bottom line - either you agree that disabled people need a bit extra, or you don't. I am curious to what those people who do not think disabled people need financial support think we should do?
I think we should be striving to reduce how many people are long term chronic illness sufferers, via better, prompter, more put together health care, and make sure disabled people of all types have the adaptations, housing etc that they need to be as independent as they can.
For example - a national standard that all new build properties have 36inch wide doors, flat access to the ground floor and a downstairs toilet.
That would make it much easier for people to find accessible homes, and stay put in them into older age.
Go further - make all these properties have space for a through floor lift and/or stair lift, and a full downstairs wet room.