They exist

and in fact, I have an Android tablet in my backpack right now

but a lot of people felt that they were going to become a major computing paradigm, and that hasn't happened.

In practice, the PC today is mostly a conventional laptop. Hybrid laptops with touchscreen exist, but they aren't the norm.

Mobile OS tablets also exist, but they haven't managed to take over from smartphones or approach their marketshare, and there are fewer options on the market than there were a few years back; "mobile OS" tablets today are mostly, as best I can tell, a specialized device to use for video-watching with a larger screen than exists on a phone, with a larger screen and better built-in speakers, but without the sensors and radio suite. Not all that much uptake.

I've seen that project. Complete radio silence since the announcement and zero path to releasing anything.

It really sucks.

I really liked my old brother laser printer.

No, a helicopter is a flying vehicle that can't drive on city streets. A flying car is a street legal vehicle that can take off and land like a plane. https://youtu.be/a2tDOYkFCYo for an idea of what I'm talking about.

Doesn't matter if cold fusion is a scam or not. People keep trying to make it work which fits OP's question.

It's quite bad at what we're told it's supposed to do (producing reliably correct responses), hallucinating up to 40% of the time.
It's also quite bad at not doing what it's not supposed to. Meaning the "guardrails" that are supposed to prevent it from giving harmful information can usually be circumvented by rephrasing the prompt or some form of "social" engineering.
And on top of all that we don't actually understand how they work in a fundamental level. We don't know how LLMs "reason" and there's every reason to assume they don't actually understand what they're saying. Any attempt to have the LLM explain its reasoning is of course for naught, as the same logic applies. It just makes up something that approximately sounds like a suitable line of reasoning.
Even for comparatively trivial networks, like the ones used for written number recognition, that we can visualise entirely, it's difficult to tell how the conclusion is reached. Some neurons seem to detect certain patterns, others seem to be just noise.

AI is great, LLMs are useless.

They're massively expensive, yet nobody is willing to pay for it, so it's a gigantic money burning machine.

They create inconsistent results by their very nature, so you can, definitionally, never rely on them.

It's an inherent safety nightmare because it can't, by its nature, distinguish between instructions and data.

None of the company desperately trying to sell LLMs have even an idea of how to ever make a profit off of these things.

It can't really reliably do any of the stuff which it is marketed as being able to do, and it is a huge security risk. Not to mention the huge climate issues for something with so little gain.

The cost to maintain it? The enviormental impact? The impact its enormouse energie consumption on everyday people (rising costs imensly)?