In the case of a normal light switch, for example, two cable screws rather than one per wire would be safer than one as the cables are less likely to come adrift. This would easily be affordable for the manufacturer and the buyer, and well within the abilities of the manufacturer. And yet no light switch has those.
And every aircraft manufacturer could think of something the costs $20 billion to develop and adds safety but they don't, unless the product is unsafe already The one crash a year is, to be fair, solidly in the unsafe end of the spectrum, but would they spend the same to avoid a once in 10,000 year crash and if not, what's the cut-off? There must be a cut-off or it would be impossible for any manufacturer of anything to make any profit, ever, as all spare cash must go into safety system research. And this is demonstratively not what they do.
Boeing has a slightly different problem in that they actively made something less safe and lied about it. They'd have gotten away with it but they flubbed the execution with a single point of failure, which made it easier to line up the Swiss cheese holes and the rest is history.