In almost all industries you start out doing low level technical stuff and then over time transition to working with people. An analyst at a management consultancy, a bank or a hedge fund spends his time looking at balance sheets or excel, whereas partners go to meetings and dinners with clients.
In a word, you make more money by transitioning from hard skills to soft, and since most developers are unwilling or unable to do this their salaries will plateau.
But compared to the financial industry, and probably law, developers can count themselves lucky. Those industries work on an “up or out” principle, sticking around for 20 years as an analyst simply isn’t an option, no matter how good you are.
Think you nailed it here. For example, in the consulting world you can pretty easily calculate the dollar value of employees at different levels based on the rates you can charge for them, the hours they bill, the new revenue they bring, and their compensation. That calculation tends to put a pretty hard limit on salaries for people not willing/able to make the transition to highly billable SME or partner-type business development/practice management.
In more traditional corporate roles, the compensation path is tied pretty heavily to growth in managerial skills and subject matter expertise in ways that don't always have parallels with software development. Even there, though, I've started seeing similar "ageism" as the article points out come into effect. Clients I've worked at have started coming to the realization that younger and more tech-savvy workers can often get to, say, 75% of the value of a 20-year employee for half the price in compensation.
I would argue the same thing does happen in other positions - salespeople usually cap out at some point or go into management (Though it can be a little odd since they have a commission portion usually. If you're really good, there's not really a cap, but functionally...). Surgeons and lawyers generally cap out unless they end up especially prestigious, but it's high enough that it mostly doesn't matter.
It's a bit different, since there actually is a fall-off with age in sports. A 45 year old basketball player is almost definitely more injured and less capable than a 20-year old. In most sports, you get better for the first 5-10 years being a pro and then it's all downhill from there.
Though, like tech, your trajectory at that point is usually management, analysis, or teaching.
In a word, you make more money by transitioning from hard skills to soft, and since most developers are unwilling or unable to do this their salaries will plateau.
But compared to the financial industry, and probably law, developers can count themselves lucky. Those industries work on an “up or out” principle, sticking around for 20 years as an analyst simply isn’t an option, no matter how good you are.