Do they, though? I mean, yes, sure, with current hardware this is true, but is this a true necessity, or an artifact of the fact that modern hardware is designed to be used by von Neumann machines?
Honest question, I don't know enough about hardware to have an answer. Can there be "functional hardware", or perhaps more practical, "dataflow hardware"?
I think this is also why pure functional languages are so hard for "normal" people to understand -- their basic premise is the opposite of the real world around us that's filled with stateful physical objects.
Having said that, a lot of non-programmers use graphical dataflow languages all the time, so maybe dataflow is ACTUALLY easier (at least for non-programmers - maybe the mathematical feel of imperative code attracts us programmers to it?) - eg, graphics tools often have dataflow languages for defining animations, materials, lighting and so on. I once used a dataflow tool for generating 3D visualizations and it was very intuitive.
A modern processor will look at the incoming instructions and execute whatever it can without creating a hazard, this is called out of order execution.
A very simple example is user input and output: I want to print the prompt text before I let the user type their input.
The same is true for plenty of other hardware: I need to move the robot forward before I turn on the drill; I need to print page 1 before page 2 - etc etc. There are plenty of inherently sequential operations, thats all I was trying to say. ;-)
But you are not incorrect - obviously there IS some hardware which is only sequential because it was designed for von Neumann machines to drive it.
Dataflow hardware can exist (there are, or were, dataflow processors made) and hardware itself is inherently dataflow. In fact, VHDL and Verilog are inherently dataflow languages (possibly) running on FPGAs, which I guess could be seen as a sort of low level dataflow processor.
EDIT: @scott_s: Sure, but the end effect is the same, isn't it?
Meta talk: responding to my post instead of editing yours makes more sense to me. First, I'm more likely to see it, and second, now I'm in the awkward position of replying to myself. I also find it disheartening that someone downmodded your comment from 2 to 1, presumably because I corrected you, but probably unaware that I was the one who upmodded you to begin with. Your point was valid, I just wanted the record to be accurate.
Sorry, HN wouldn't allow me to reply to your comment for some reason, so I edited mine.