This is how consciousness seems to be defined:
Consciousness, at its simplest, is awareness of internal and external existence
Some dogs seem to be aware of internal and external existence, as do many other species of animal.. or am I completely off on that? If I'm not, the bar for consciousness seems rather low. All you need is a complex enough neural processing pattern recognition thingy that we call the brain. Not all complex brains will lead to consciousness, but many will.
Where does it come from? Surely from our biological brains, in some capacity. Have you ever seen something conscious that doesn't have a brain? There seems to be a strict 1-to-1 correspondence between consciousness and a complex neural processing thingy. If you have that thingy, you can have consciousness. If you don't, you can't. Yeah, I get that this doesn't
really answer the question of where
exactly consciousness comes from. We don't understand the process and all the nuances of consciousness. But nevertheless, the neural-processing meatsack known as the brain sems to be the source.
No machines have consciousness yet. The "AI" you see in use today are just language processing models. They are not aware of anything, whether it's the external or internal.
Can machines have consciousness? Sure, I don't see why not. We are biological machines after all, are we not? There doesn't appear to be anything inherent to carbon-based biological constructs that a silicon-based or whatever-based machine couldn't replicate, in theory, assuming the chemistry and physics work and no natural laws get in the way. Could some natural law get in the way, something with the way chemistry works in our bodies that a machine couldn't replicate? Sure, but all you have to do then is build a machine brain out of the same parts that our brains are made of. So machines having a consciousness seems a possibility, assuming we can figure out how to construct such a thing. I suspect we will get there one day.
Why do we care? It helps us understand who and what we are. That's sort of an integral aspect of the human experience, it seems - analyzing our existence and the world we find ourselves in, what it all means, if anything, what we are, where we came from, where we're going, etc. Also the question of: "Are we unique, and if so, in which ways?". That's something philosophers and stoners have been asking for centuries.