Most people I know who are on UC or PIP or were on JSA etc in the past would have much preferred to work and were either completely unable to find or to do a job.
I've known a number that I was less comfortable with. Deliberately performing badly in interviews for jobs they didn't really want, because they were holding out for a dream job however unrealistic. I think that it's right to get work as soon as possible when society is giving you money to sustain you whilst unemployed.
And a others who could manage some work (albeit not a permanent full time job), but who couldn't afford to mess up their benefits by doing bits of work here and there. And that's a problem with the system, when it's effectively discouraging work.
Plus a few with mental health problems which I suspect would be helped by the right kind of job, long-term. Unemployment is often unhelpful for those prone to mental illness.
As I said, it's a very small number, both a tiny proportion of claimants (anecdotally IME, and more importantly statistically), and I would say that I've known more people who are dodging tax than wrongfully claiming benefits.
I also know people who've really deserved PIP but had an awful time getting it. No idea how to solve the problem of dodgy claims and unnecessary claims without making life even harder for people who genuinely need the support and already have incredibly hard lives.
One thing I'd do though is to mandate a minimum level of child support payable by the non-resident parent to the resident parent, deductible from income if it's ever in arrears.
If the NRP can't or won't pay, the government gives the money to the RP and then claims it back from the NRP, court enforced with penalties if necessary. It would be a debt that cannot be written off, much like student loans. If income is insufficient, it should come from assets.
I think this would lift a huge number of children out of poverty. Not exactly benefits I know, but certainly related.