No it's not about pity money at all. It's about arithmetic.
Currently there are 3.1million DLA claimants at the cost of £12 billion pounds annually. source
The projection is that by 2015 this number will go up to 3.5 million meaning if there is no reform/increases and not accounting for inflation, DLA will cost us £13.5 billion.
Given the government is spending £150 billion or so more than it is taking in tax, we simply cannot support 3.1 million people, let along another 400k!
So...we now have to make some crap choices. We either find/borrow another £1.5billion a year from elsewhere or we have to say to some people who currently get DLA "Sorry, we can no longer support you".
That conversation is basically inevitable.
What I don't agree with is the current process which is flawed.
But it doesn't change the fact that we cannot support the same number of people as we do. In fact we never could. The only reason we 'could' is because we took out huge loans and continue to do so.