Hi,
In 2000, I, and 5 others, were "laid off" from a 22 yr job, others had longer time. My department had only 1 employee, me; the Quality Control Manager.
The company called it "Reduction in Force; Permanent Lay-offs". All of us, at that time, were 50 or over! Companies do this to reduce insurance payments, of older workers, and get by with it.
Another reason is that the company may no longer need a particular position, and lay off a person. Others, then have to work harder to "cover" for the person laid off; ie, do their work as well.
I, also, had no indication that my lay-off was coming....no warnings of any kind, no oral or written warnings about my work, cause it was excellent, with annual reviews showing excellent.
Just to go one step further, some companies now are "reneging" on their promised retirement plans....cutting back on money being paid out, and increasing employees' contributions to retirement, out of the employees' pockets.
I am so sorry to hear about your job, but unfortunately, companies do it. It doesn't sound very appropriate, but they get away with it.
Others will be along to add to my answer for you, and hopefully, will have some more positive advice. I would immediately update my resume, and start looking for Classifieds, and from other employment sources. I do wish you the best of luck.