I think the thing is that many photographer FOUND them worthwhile in the past, and often had one or two very reliable agents. They are not quite as badly affected as the article implies by new sales models - for example, in the first week of July I have six sales through Alamy totalling $459. The main issue for me is not the library/portal itself, but the dishonesty of the end users with accounts. I'm seeing too many pictures used in the national press and then simply never paid for until I complain a year later and get Alamy to chase the payment.
Considering these uses are ones I find, sometimes by mistake or tipped off by someone else, I have no real idea what other unpaid uses may be out there. And it's very frustrating to have pictures in international news and magazine media, and only receive the equivalent of maybe £15 for the use - or zero!