That's not to say that system of checks works. Places like Florida have enacted mandatory drug testing for welfare recipients, so there's obviously some political will to punish and regulate the poor.
All it would take is the right political climate and circumstances, combined with ad campaigns and lots of lobbying. Many arguments would be put forth to convince people a minor change is a good thing, that due to the current circumstances, its necessary. Many people would likely agree, despite the risk it opens up the potential for the system to be abused with another minor change in the future. And its voted through by popular demand.
A few years later, the political climate changes and the government isn't perhaps as trustworthy/predictable as it might have once been.
Now of course it could go the other way. However, power creep rarely goes backwards.
which is, ironically, the kind of Big Government bullshit the right-wing in this country claims to want less of. it's hypocritical.