There are many reasons committee officers choose to do the work of external managers themselves. Often it’s a case of wanting to make a contribution or be hands-on, other times it’s about control.
If I were the professional manager I would be asking if my people were being given the opportunity to do the work, if they had failed to fulfil the terms of the contract and what would happen if the chair sold up or just couldn’t do it any more.
If I were on the committee, I’d be glad of the flexibility in this arrangement, knowing that ther was a fall-back when the voluntary work ended and a benchmark for what was expected of the managers in the future.