There was a short period where external GPUs that could connect to your laptop were kind of big a few years back. The never really took off though, and that was the only big component I saw that with.
They often just don't justify the cost. The enclosures themselves are expensive, and there's a really rough performance hit, less than half the framerate of the same card connected via PCIe in some cases[0]. A decent gaming laptop probably costs about the same while having better performance[1].
They're not particularly portable either, so you'd be better off getting the gaming laptop, or building a desktop with a cheaper GPU for roughly the same price.
The size/power delivery of the enclosure can be a limiting factor as well, new GPUs have tended to be bigger and more power hungry, resulting in many enclosures just not being compatible with newer cards.
The cheapest egpu case I could find is 300 Euros and that's just the case with an internal PSU. You still need to buy an incredibly expensive GPU to put into it.
So now you're spending probably 1k just for the laptop, plus 300 for the case and an additional, let say, 350-400 on the GPU.
For that amount of money, most would probably look for good laptops that have an integrated one, buy a handheld, a console, or just don't want to spend that amount of money on it.
