There are corporations that over-hire and often provide no work at all for weeks or months, but they require that worker is always on stand-by in case there is a surge. I know full-time workers who throughout an entire year maybe done one or two small PR-s, but when suddenly there is an issue needing solving and product teams have full capacity, these people save the day. They are sometimes also utilised for pairing, when given product team members have no spare capacity. From someone not knowing this, they indeed may seem like deadbeat employees, but the key is - they have to be always available during work hours even if no one contacts them for weeks.