From the doc posted by Chronus: ECA maintains that in reality 'self-employed' pilots are forced to accept this status, while working for only one airline. They reportedly have no control over their remuneration, working time or places of work.
Cobblers. Well, qualified cobblers...
Sure, I'm sure that if we think long and hard we might be able to think of an operator or two that take the piss by the use of various schemes but that's no reason to ban outright a way of working that serves many of us on both sides of the contract very well indeed.
Having been happily self-employed and freelance (usually for three AOC operators at any given time plus some private work) for 20+ years, in the same circumstances I'd choose it again in a heartbeat over being tied full-time to just one operator. Would I always choose self-employment? No - but the salary, roster and conditions would have to at least match the income and lifestyle that being freelance has made possible - which are both far better than anything anyone has previously managed to set on the table.