We don't move quite that often - we're usually on two-year cycles, so we just sign standard 1+1 leases. As one of the sibling comments said, the local market heavily influences the housing stock and we've always been in big expat-heavy cities where renting furnished places is pretty common.

It's also a thing to negotiate furnishing with the landlord, e.g. I'll pay an extra $100/mo in rent if you agree to do an Ikea run and you can keep it at the end of the lease.

If I need to be somewhere for <1y but >1m, I'll try to deal directly with AirBnB hosts but sometimes you just have to eat the borderline usurious serviced apartment fees.