they usually recruit their staff through the jobcentre, jobseekers are browbeaten into taking this kind of work with the threat of sanctioning.
I'm a service manager in the care sector and in my experience, people who've been sent our way by the jobcentre don't even show up. The jobcentre doesn't seem to have any way to check if they've attended or not, only if they got an interview. Regardless, I certainly wouldn't employ anyone I thought wasn't suitable, but with care/support work being low paid and low status recruitment is very difficult, and getting worse.
I'm fortunate that I work for a nonprofit, and have spent most of my social care career in nonprofits. The exception is my last employer, who were pretty bad - they allowed a neighouring home to go from Needs Improvement to Inadequate over the course of a year without any action from senior management, took on placements that were totally unsuitable and were just basically all about the money. They left me with a firm belief that it's immoral and inefficient to run care services for profit.