Essentially, tablets are an answer looking for a question.
The mobile tech industry has a problem: the perfect form factor was invented in the early nineties.
Although the first laptops were super bulky and not very usable, it was clear from the beginning that the clam shell was a perfect form factor.
It cuts the area of the device in half, gives you a perfect input device right off the bat (with supplementary input methods like trackpads, trackpoints and touch screens coming later) and it's small and light enough to take everywhere.
Then Apple popularized the smartphone, and used the same technology to make a larger smartphone that couldn't make calls. People bought it like crazy, but the problem remained: iPads (singling out iPads here because other tablets are pretty much irrelevant) can't do anything a laptop can't do better, except in extreme edge cases.
You find people here being so enamored with their iPads that they use all kinds of crazy workarounds to make iPads their main computers, like buying Apple's terrible keyboard, without realizing that once they added all those fancy accessories, their iPads are as heavy and as expensive as a laptop.
And then, congratulations, you just spent a thousand dollars on a laptop that runs a phone OS, can't be used on the lap, can't be used with one hand, needs help standing upright, has a bad aspect ratio for the one thing people say the iPad works well for (watching videos), is slower for any productivity task and doesn't fit into your pocket.
I would argue that laptops are at this point less useful for me. I work with a 2016 MBP and I wish Apple released a tablet version of it so I didn't have to deal with that **** tier keyboard since I carry a 60% size mechanical keyboard with me to get around that issue. A Surface Pro type device capable of running OSX would be ideal for me. In fact if Apple doesn't fix the various issues with the current MBP by the time I am due for an upgrade, I might just get a Surface Pro and use that. A lot of laptops suffer from issues like crap keyboards and trackpads and many cheaper non-Apple ones have gobsmackingly **** displays.
For travel abroad I like carrying an iPad instead because it's lighter and takes less space. So far it has done everything I previously used my laptop to do. I just use the virtual keyboard now but used a keyboard case with my Air 2. My gf uses it to take notes at school, again doing nice double duty as a laptop replacement and something you can fold and use as a media consumption device.
I don't want a laptop at home. It's not convenient to use on the sofa whereas I can just grab my iPad Pro and lounge around with it wherever I want better than I could with a similar size laptop. For heavy lifting I have a desktop PC. Two-in one type devices like the Surface Book are probably the ideal marriage of laptop and tablet but few manufacturers make them.