They’re only important if the next stage is a plan to go to more rigid, higher production capacity methods. Injection molding demands thorough care with draft angles to enable smooth ejection. Building them saves time for knock-on design changes later. Your model would closely match the final part. For a prototype or one-off design, they’re basically of no value. Silicone molds are so flexible they allow you to focus on part function without worrying about extraction. However, where a part’s geometry has deep or sharp features, adding draft angles might extend the mold's service life by reducing stress.