On a personal level, I’d never use them anyway because I don’t bid for work. I’ve found that the better the platform and network a writer’s built, the less they’ll need to rely on those types of services and the less likely they’ll have to worry about getting paid. The security’s there as a reputation’s built, and probably even moreso than with freelance marketplaces. They’ll never compete with a solid referral base. That said, I know some writers still prefer them because they’re comfortable with them for whatever reason, and that’s fine too. Just don’t allow that comfort to mean you’re willing to be disrespected as a freelance professional by being required to make allowances you should never be asked to make (speaking specifically to US writers and in regards to that absurd monitoring ability).