Flash - saviour of the universe....
Or not, as the case may be.
But I digress. The revelation that there are insecure unpatched installations out there is a bit like making proclamations about the toilet habits of bears that frequent forested areas. Flash is very common on home devices, but probably less commonly used than it used to be. If its update function fails, most won't know/care. A bit like the free couple of months of Symantec abandoned on home PCs by users reluctant to pay for AV.
It's no worse than Java, where old versions are often retained simply because backward compatibility is often a problem.