For some applications, getting it wrong – or not fully optimal – the first time can be very expensive. For example, when making a semiconductor, it is very expensive to re-make masks. Plus, of course, if the semiconductor has already been put into another device, such as a camera, or mobile phone, or set-top box – it is too late (except perhaps for software workarounds). Also, in the field of semiconductors, there is a trade-off of extra silicon area for more advanced processing, versus the cost of designing and supplying a larger chip.
Another excellent primer from Tek - well worth reading if you're involved in digital video delivery.