A general reason to focus on abuse instead of immediately visible outcomes: if the abuse is not dealt with properly, then that may lead to the abuse becoming increasingly widespread and blatant, which will affect future outcomes.
https://ifs.org.uk/publications/health-related-benefit-claim...
You can argue that nobody is systematically abusing the system but numbers go up. To those paying the taxes to support these benefits that sort of growth looks like abuse.
Yes, but for 'tax payers' everything looks like abuse until they benefit from the services for which they pay taxes. The favorite hobby of people whose identity is shaped by being a taxpayer is to complain about paying taxes.