First, it is already the case and has been since the 1996 welfare reform bill that you can't stay indefinitely on welfare without looking for work.
Second, according to the census page linked to from your wikipedia article, 37.1% of those in this quintile are aged 65 or over, while 58.7% of such households have no earner. If we assume that seniors are not working and should not be required to, and that they live in their own households (which are of course simplifications which have exceptions), then this means that in fact a majority of households with someone 15-64 in this quintile
do have an earner. This even includes those households where people are disabled, single mothers at home with newborns, etc.
Third, it should be obvious that not everyone who has no job is unwilling to work or is not looking for one.
Fourth, do you not believe that we enjoined thus?