Real Estate on a satellite is extremely expensive, and every owner of every Payload needs to be assured that another Payload will not fail in a manner that will adversely affect their own project. Data acquisition of one payload is often dependent on data from other(s), adding to the pressure that an instrument must not fail after launch. Multimillions of dollars are at stake. Thus, companies who manufacturer space instrumentation (including satellites themselves) have to subject their products to Prototyping, and Flight Verification phases.
