Why are the sign conventions of work done in thermodynamics different for physics and chemistry?
The difference can be understood by looking at the history of development of Thermodynamics .
During the initial stages of industrial revolution the main focus was to get the work done by a machine the more the work done by the machine the more beneficial it was thought to be . Thus it assumes a positive sign for work done by the system as we are measuring the work done by the system (Machine).
On the other hand chemistry deals more with changes in the composition of the working fluid or composition of the system-surroundings more in general. Thus, work done on the system which brings about changes in the system is considered positive