Instruction manuals ought to vary in size and detail with the complexity of the technology in question. Therefore, a car has a very detailed manual because it's a complicated piece of machinery, while a desk lamp has very minimal instruction because it just has one switch and one function.
This isn't actually how things work, though. For one thing, sometimes we don't use all the functions of a thing: my desk phone at work came with incomprehensible instructions because it does fancy things, but I literally just use it to dial numbers and answer incoming calls. My washing machine came with a booklet but I just turn the thing to the same option each time and press 'on'.
Other times, the manufacturers have just made the instructions unnecessarily complicated: my slow cooker just has one knob with Off, Warm and High but it needs a booklet of explanation so you can't sue them if you electrocute yourself or whatever.
And sometimes, it reflects a change in our relationship with technology. Here's a photo of a hand dryer in the Quarterdeck in Margate (there's a side note about my collection of photos of hand dryers which I will relate at the end of this post):
As you can see, it has the following instructions:
Shake off excess waterI expect that these instructions seemed fairly minimal when the thing was made, probably about 20 years ago. Now, though, I think this is more instruction than anyone really needs - we all know that you stick your hands under a dryer to make it work. We are used to things starting automatically. I doubt anyone except me reads these instructions and certainly not before they've already done what they say.
Place hands in dryer
Compare this to something like a smartphone. Mine came with no instructions whatsoever. That's not strictly true; it has 'hints and tips' and a 'setup wizard' built in, which are instructions. But there was no manual. I can't remember what the first piece of tech I bought was that came with no manual, but I do remember it feeling a bit weird (it was on a CD that came with whatever it was). We are used to things now - we know that to work a gizmo you press the 'on' button and see what happens. Everything more or less works the same, and as you would expect. Things are relatively intuitive. So we don't expect careful step-by-step instruction on how to dry our hands. And I think manufacturers have got better at writing for their audience, and anticipating what you actually want to know and can understand.
So, that side-note. I have a collection of photos of hand dryers in Margate establishments because, adorably, the hand dryers are mostly made by this local company, Arlington Supreme. Everywhere else in the country, they're made in Honeypot Lane, Stanmore, Middlesex, HA7 2PY (yes, I know that from memory - if I look at words for long enough and enough times I apparently commit them indelibly to memory).