I get pretty irritated when people say, in an offhand casual way, “why didn't 'they' simply do XYZ?” Or, “why didn't they just add ABC to the product? It would have been easy for them to do it”. While I generally welcome suggestions, it's the “easy” part that annoys me.
Very few designs and user interfaces are easy, there are almost always multiple, overlapping, conflicting factors for the designer to consider. I saw this first-hand when I was part of a conversation with some mechanical engineers (MEs), and the question of material selection for a small structural member came up. One of the electrical engineers in the group (thankfully, not me) remarked “that's no big deal, it's just a piece of aluminum.” The ME's face got red, and he brought over a book detailing the industry's standard aluminum alloys along with their key characteristics: basic tensile strength, fracture resistance, machinability, ductile parameters, flow and creep, corrosion resistance, surface finish, and much more . Then he said in a very direct way, “OK, smart guy, which aluminum?”
I spent some more time the next day with that ME, and looked at a basic finished-part dimensional drawing he had. I asked him about it and he said that it looked simple as a drawing, but it was a difficult decision to make on how to fabricate the part. They could machine it from a larger billet, they could rough-cast it and then final-machine it, or they could do a near-final-form casting needing minimal machining, among other choices.
Not only were there the usual cost issues, but there was also some implications for the part's in-use performance, depending on how it was fabricated and the resulting internal strains and material grain flow. None of these issues were evident from the dimensional drawing.
So next time someone says “no big deal, why don't you just add a resistor/capacitor/inductor there?” be prepared. Just ask them what kind of resistor they had in mind: thin film, thick film, wirewound; what voltage; what current and power; what frequency; what package? Just because it's easy to say doesn't make it easy to do.
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