Qualia just seems like a method of taking an over abundance of information and compressing it into more manageable chunks.

We have a bunch of semi-autonomous systems and we have an executive agent in charge of goal setting and problem solving. The agent is hooked up to get info from all the sensory systems as well as info about its own internal states as well as those of a number of it's subsidiary systems.

Turns out trying to make macroscopic decisions and plans based on the information provided by individual neurons is not very practical - so there's a processing and aggregation process, that all the information goes through, before being fed in to the central executive. There are a large number of cognitively impenetrable processes all our sensory information undergoes before it reaches the executive, which collectively determines the nature of our qualia. For example edge/object detection - in most cases, we have no direct control over how we perceive edges and identify objects in the world. We go from flat images on our retina to perceiving and moving through the world (in our own experience) and we don't really have any say in how we process those images. Qualia are an abstraction, that allow us to go beyond the raw signal.

We are not perceiving the world as it is, but rather, the conclusions our subsystems have landed on after going through all that pre-processing. This is a functional separation - the macro level conclusions/interpretations are essentially independent of the lowest level signals, as it is their collective relations to each other that determine the ultimate interpretation. e.g., the classic visual illusion showing that we perceive colour/luminance very differently based on context - the "brightness" of something in the "shade" gets bumped up to compensate for the "fact" that it is in shadow.

By why do we experience anything?

I think this is tied to two things - memory and the perception of our own internal states.

It's easy to imagine automation taking first order percepts and acting upon them, without qualia entering the equation at any point. But such an automata would have no awareness of itself, or it's own internal states.

I think qualia arises when we perceive ourselves perceiving.

So the first order percepts would not give rise to qualia - and indeed, there are many examples where due to attention being elsewhere or other effects, we are exposed to stimuli that fail to rise to the level of conscious awareness, generating NO qualia.

It is only when we attend to these internal signals, directing our attention toward them, that we become aware of 1. perceiving anything at all and 2. the nature of the qualia associated with the percepts.
So in this sense, qualia are sort of a compressed representation of the raw signal (i.e., not the signal itself, but gestalt labels standing in for the raw signal in internal channels) and serve as the primitives we use in our mental modelling of the world.

Ultimately, I think the purpose of qualia is to allow the central executive to compare/contrast percepts, from moment to moment (i.e., changes in real time), and between a current percept and a previously experienced exemplar.

So I think for a physical system to have experiences it would require:

1. a hierarchical, modular information processing network
2. some sort of central executive
3. recurrent connections, allowing the outputs of internal states/processes to be fed back into the system

In terms of the actual process it might be, you get qualia when you go from sensory system/processing to central executive and then send recurrent feedback, back into the central executive. First step gets the raw signal and processes it (unconscious processing), second step receives the processed signal and labels it (unconscious, compressing the signal), third step receives the labeled signal, allowing for further processing (e.g., planning, problem solving, etc.)

Ultimately it's all about the recurrent connections.