That is a really short sighted view of it and which is why we will always have the problem of people being on the dole. Not everyone on the dole is some scrounger who has never done a days hard work, you will find plenty who have worked and payed tax and payed into the system, from memory there is a NI contribution based dole so you get yours from essentially the money you payed in.
The welfare system is a great thing in essence it is supposed to help those who need it, for exampled the severely disabled and its supposed to be a temporary fall back for the working able when they are out of a job. Of course there are those who will milk and scam the system, there always will be those kind, but not everyone is on it to scam the system nor are they all alcoholics who have never had a bath.
In reality no one would want to live on £50 a week, that is no life, so it makes no sense for someone to scrounge £50. The problem with making them clean the streets is that it isn't solving the issue of them not having a job, what exactly are they going to gain from it? If the idea is to make them get fed up and sign off, then the scroungers who are just milking the system will turn to criminality, the ones that aren't will just fall into poverty.
Why not actually create jobs and match dolers to these jobs, send these kids to some sort of training so they can learn a skill etc. Basically get them doing something that will actually get them a secure job and off the dole for good.