It's partly because of the technological skills as mentioned in the article as well as looking for long term employment as well as health care costs. Older people are more expensive to put on new insurance.
I'm not saying it's right to discriminate against them but it is something they do consider.
Crap, frankly. Age discrimination has been alive and well in the U.S. ever since it was outlawed. Companies find euphemistic means of getting around it, and anybody who has worked for a big corporation goddamn well knows this. You get to fifty, you're on the short list for RIF ("reduction in force"), and that's the way it is. Management can always justify this in some manner. I took a voluntary separation package from BP at the age of 48, recognizing that it was time, and the involuntary package that would come in a year or so wouldn't be nearly as good. Plus, they were threatening explicitly to transfer me across the country to a place where they could jettison me with no difficulty. I had a lot of seniority; I cost too much. Didn't matter than I had the experience that made me better at my technical job than anybody else they could get for less money.
Then I set up a consulting business, and BP hired me back and paid me 50% more money than my previous salary, because nobody else could give them the services they needed. I was out of work a week (nice vacation), and put back to work in the same goddamn Dilbert cubicle I had dwelt in before. And didn't need to attend idiotic staff meetings or fill out idiotic evaluation forms, etc., etc., etc. But consulting fees came out of a different budget than employee salaries, and I didn't show up on employment rolls. This all made complete sense to the accountants who ran the show.
I took the money with no angst.
This kind of shit happens all the time, in every major industry.