People who do workfare have been unemployed and receiving benefits for some time, they don't make yo do a mandatory placement the moment you sign on for JSA.
I can see the benefits of doing unpaid work experience like in the example given of the lady in the museum, but I can't see what more she would have got from continuing to do this voluntary work indefinitely that she wouldn't have already had from the first couple of months when she was on JSA and not required to do any work placements.
She could also have continued to do the voluntary work around the work placements, or if she was in employment. Life doesn't make people choose between voluntary work or paid work, plenty of people do both.
I don't like the idea of taxes subsidising big companies to have good quality workers that they could be paying for themselves, but not everyone who does these placements is a good quality worker. Sometimes they are people who have no work ethic, no experience of even getting up at a regular time each day, let alone to go to work, and I don't think companies should be expected to try and manage and train those people when there's no benefit to them.
There are situations where workfare is appropriate, and a good use of taxpayers money, and there are times when it isn't, but clearly, expecting a little common sense to be applied seems to be too much to ask for.