Perhaps some translators feel good thinking that they are collaborating with the translation brokers they depend on for work.
Translators are not collaborating with translation brokers. The term collaborate implies that both sides are contributing. Most translation is sold by translation brokers that are incapable of becoming involving in the translation process, beyond purchasing a translation from a translator and reselling it to a client. Even when a translation broker performs some intermediate processing on the translation they purchase before reselling it, that processing is usually also a service that they outsource (purchase) and resell as part of the translation. There is no collaboration in sight.
Translators sell translations to translation brokers. They are no more collaborating with translation brokers than a chicken owned by a chicken farmer is collaborating with the farmer when the farmer takes an egg from them and throws them some chickenfeed.