Because of the same elements that make it strong. 5.5-6.5 % aluminium and 0.5-1.0 % titanium form a high volume fraction of gamma-prime Ni3Al, and that precipitate cracks under hot working. 713C is melted and cast, and it is supplied as remelt stock and cast bar for investment casters, not as wrought bar or plate.
The metallurgy in one paragraph
Gamma-prime is an ordered Ni3Al precipitate that is coherent with the matrix. It is what gives the alloy its creep strength at 900 °C and above, and it is the reason the grade exists at all.
The catch is that a high volume fraction of it leaves very little ductility at hot-working temperature. Forge or roll the ingot and it cracks rather than deforms, so the wrought route that produces 718 bar does not exist for 713C.
What that means for the order
713C is bought as remelt stock — electrode or ingot for a foundry's own vacuum melting — or as cast bar. The relevant specification is AMS 5391, and the delivery condition is as cast, or to the foundry's remelt requirement.
It is not supplied as wrought bar, plate, tube or forging, and a quotation promising those forms should be questioned.
Where it is the right answer anyway
Equiaxed investment-cast turbine blades and vanes, industrial gas turbine nozzles, and turbocharger wheels — parts that are cast to near-net shape precisely because machining or forming them is impractical.
If your part needs to be forged or rolled, the answer is a wrought grade. 718 covers much of the same temperature range with a fraction of the strength at the very top end, and it machines and welds. The choice is between casting for strength and wrought for manufacturability.