Experience levels
Experience is often misunderstood, particularly by the people who think programming is a young person's game.
In the early 1980s, when went to university and entered the industry, the amount of experience needed to be a valuable contributor was pretty low.
At the time, many of the programmers - especially COBOL programmers - had a 3 month training course before they entered industry. Many organisations took their brighter filing clerks, sent them to training for 3 months, and now had a staff of programmers.
Our university courses managed to cover a large % of the known universe of computing. It was a big step up from the 3-month programmer. A graduate was a pretty valuable and useful thing.
These days this no longer holds true. Each field in computing has got vastly more complex and you need years of experience to be really productive.. All a degree says is that you seem to have the capability to hold your head above water and might turn into something useful in a while.
This should skew the industry towards older workers. Not all of them though. Our industry is one of constant change and people need to constantly update and refresh their skills. If I look back at the stuff I learned at university, none of it is really relevant now. I've kept up reading/experimenting at an average rate of approx 5-10 hours per week. If you're one of those people who thinks you can just sit back now you have a degree then you don't belong in this industry.
Unfortunately there are enough of the old slackers to build the "can't teach an old dog new tricks" myth whereby you need to refresh the staff to get a handle on new tech.
Companies that operate like that do themselves a disservice by removing the experience and guidance that is needed to train up entry level staff. They also shed staff that are just entering their prime.