Full disclosure: I am 56 years old.
I've found over the years that a lot of smaller, family owned or privately run businesses will hire older personnel for the experience factor alone. Granted, I'm a Sysadmin, not a programmer.
The larger companies are shackled by company policy (written or unwritten) HR, fixed pay scales and so on. I do believe money comes in to play as younger can mean considerably cheaper, but if that person takes 3X longer to accomplish the task, how much are you really saving in the long run?
The company I've worked for the last 8 years has 50 employees, 11 servers, 65 workstations, laptops, phones, tablets, and so on. I'm also involved in special projects which I have time for because all our systems run smoothly. I can take time off without fear of something bad happening, barring hardware failure or user stupidity.
I tried hiring an assistant, but didn't have much luck. Anyone who could actually help me, and was knowledgeable were few and far between. I got lots of kids who "played with computers" but had no clue on AD, Domains, and so on. I was willing to pay 50k to start by the way.
Anyway, of course age discrimination exists, as does other forms of discrimination. It has simply moved below the surface whereas previously it was overt. I know many companies I have dealt with would hire me in an instant because they know my skill level, however I would have one Hell of a time on the open market at my age. I doubt I would make it past the HR drone.