It's been a long time since I've built a computer myself, but back in the day the Intel chipsets weren't the only ones that could boot Intel processors unless I'm mistaken there were always 1 or 2 alternatives. Or is this not the case for laptop systems? And what about AMD, do they do the same thing?

http://shop.amd.com/en-us/business/notebook/20DE001RUS

They do have laptops with AMD chipsets.

Intel CPUs are tied to specific Intel chipsets these days, with no third party vendors.

AMD used to be much better (they have some small firmware for a support function that was signed, but even that was so half-hearted that one coreboot developer managed to recover the key - but didn't publish it).

These days they support ARM Trust Zone (with an ARM processor), and that part of the system is all signed (as "Trust" doesn't mean that _you_ can trust it).

It's Hollywood, essentially - can't have you crack your movie-playing device to copy their precious bits. And what else would anybody use a computer for, if not for watching blockbuster movies?

That hasn't been the case for a long time (a decade?). Nowadays you can only use Intel chipsets, even in desktop systems. I believe it's the same for AMD.