In some respects, laptops are the same as tablets. They serve a purpose, the hardware configuration is controlled by a single entity and they are relatively closed. Yet, you think they are different. The answer is that laptops have always been like they have, and tablets have generally always been in a closed state. There is nothing really 'unique' about a tablet that doesn't make it a general computing device, it just has a different input system.

Now personally I love general purpose hardware, because purposes change, and the software on the device should be able to change with it. I don't think a laptop would be viable for me unless I could change the software. You might bring up phones, but there is a reason for that. They used to be embedded systems, designed for a single purpose (and usable only for that purpose). These days they are general purpose devices that also make phone calls (even if this single purpose drives many design decisions).

I've also done crazy things like install an alternate firmware on my router, why, because it gave me more features. This is why I like general purpose devices, and my freedom to change their software to suit my the specific purposes I want. Tablets aren't fundamentally different from a computer, they just have a different skin.