Gateway to lots of other resources and benefits.
Social housing, housing benefit, council tax benefit, carers allowance, increased UC, discounts on days out, different funding schemes in education and work. NO benefit cap if you have a dependent child on DLA.
There have been several threads on MN with OPs making the equivalent of 70k a year salaries just in benefits because they had a child in receipt of DLA and were in high-cost rentals.
A poster recently who had a DH earning 67k a year and they were receiving over 2k a month in benefits with a disabled DC and adapted social housing and the OP wanted more as wanted to register for carers allowance looking after her MIL.
That's why it's a trap. Several hundred a month may not be enough to live on if claiming PIP but the extras it can help entitled people to means they're reliant on it and have no incentive to get into work or get better because once they're not receiving it, lots of other benefits fall away.
When David Cameron the multimillionaire was PM he was claiming DLA for his severely disabled child who later sadly died because he said it gave access to other things they needed. Including the 4 nappies he claimed per day from the NHS.