I realize this point might not be obvious:

Adults in immigration detention are not entitled to be appointed a lawyer.

To win attorneys' fees, the immigrant has to hire a private lawyer. That lawyer has to file a habeas petition. They have to win the habeas petition. A court has to find that the detention was unlawful. Then, they have to move for attorneys' fees as a sanction after the case is over, and it's an uphill battle to win that.