We might easily build tiny chips that don't make much heat, that do more limited tasks incredibly fast. That could be packaged "like a wide spot on the cable". We don't, because we choose not to.
Well, small and low-power chips do exist for various applications.
Microsoft chose not to continue making Windows 3.1 available, and so people have had to buy larger and more powerful microprocessors, instead of smaller and cheaper ones with the same power, to have desktop computers that can run current applications. Windows 3.1 could run in 2 megabytes; to use the X Window system, even with fvwm and an old version of Linux, took 16 megabytes.
I guess we could choose to use computers like the original Asus Eee, for example. But while the current situation is the result of choice, it's choice in a marketplace where what is available and what everyone else is using strongly constrains the choices of individuals - it's not where people are individually choosing the current kind of computer, from an assortment of equally viable alternatives, as the best kind of computer for them.
Thanks to viruses on the Internet, people can't even opt for the strategy "I've got Windows 98, I can play DVDs on my computer, who needs to upgrade".