Because you don't want to buy a computer from a company that might not be here to support it. Much of the Windows PC part of the industry is starting to look like a bunch of "fly-by-night" operations. That doesn't generate much trust, and chrome books would do better if they didn't emulate the strategy.
I didn't realize that Dell, HP, Samsung, Sony, Lenovo, Toshiba and Asus were going out of business due to the lack of profits. I never looked upon these companies as "fly by night". Should I hope that my electric company makes a healthy profit at my expense too?