If you're a tech critic like me, you discover one thing about technology fans right away. They can be fairly militant in their allegiance to one tech company or another.

As you read readers' objections to a review you've written, you encounter one particular argument amazingly often: “[Name of disliked tech company] stole that idea from [name of preferred company]!”

Absolutely right. The borrowing of tech ideas has become almost absurdly predictable. Apple introduced Siri, the voice assistant, in 2011 (after buying the company that developed it). Google's copycat, Google Now, arrived a year later, and Microsoft's Cortana followed in 2014.

In the era of Steve Jobs, Apple was often the first to develop new product types. The iPod, for example, begat the Microsoft Zune. The iPhone spawned Google's Android phones. The iPad was the model for everyone else's look-alike tablets.

These days, though, Apple is equally likely to be the follower as the leader. Samsung's Galaxy Gear smartwatches debuted in 2013; the Apple Watch arrived two years later. Spotify reached the U.S. in 2011; the nearly identical Apple Music launched in 2015. Microsoft's Surface tablet arrived in 2012, with a screen cover that opened to reveal a flat keyboard. The iPad Pro, with similar features, followed in 2015.

It's not just product ideas. You can find the same cycle of mimicry in individual features. You could easily create a genealogy of, say, the right-click shortcut menu, or notifications that pop up in the upper-right corner of your screen, or precisely three autocomplete suggestions that appear above the keyboard on your phone.

At the dawn of tech culture, all of this might have seemed like an outrageous theft of intellectual property. It certainly did to Apple, which famously sued Microsoft for duplicating the Mac's “look and feel” with Windows in 1988.*

But Apple lost that lawsuit. The central premise of copyrights (for creative works) and patents (for inventions) is this: you can't protect an idea—only the execution of it. That, in the end, was the crux of the court's ruling in Microsoft's favor. (Never mind that the features Apple was proudest of—overlapping windows, commands in menus, and so on—were originally developed by Xerox and found their way into Apple's machines.)

For a while, copycats paid at least lip service to differentiation. In Windows Vista, Microsoft added a universal-search icon like the one on the Mac—but placed it at the lower left of the screen, not the upper right. It created little floating windows showing stock, weather, notes, and so on—but called them “gadgets” rather than “widgets,” as Apple had.

Today, though, nobody even bothers. Amazon's popular Echo, introduced widely in 2015, takes the form of a cylinder that sits on a shelf and does an enormous range of tech tasks, from streaming music to answering questions in response to spoken commands, like a home version of Siri. This year Google revealed its own Google Home—which works so similarly, it could almost pass for a clone.

First problem: Apple, Microsoft, Samsung, Amazon and Google basically wind up with identical portfolios: similar phones, tablets, laptops, music services, e-mail services, payment systems, auto-dashboard software, etcetera. Bigger problem: This frenzy of idea stealing thwarts innovation. It's time-consuming and expensive to develop a new product. Copying, on the other hand, is cheap and easy. So why should a company bother to innovate? You don't reap much benefit from being first, except in the few months before the copycats come.

Pharmaceutical companies enjoy 20 years of patent protection before generic drugs are permitted; the idea is to let them recoup the billions they've put into developing new medicines. Maybe we should adopt a similar structure for tech products—with a period of exclusivity of something like 20 months.

That way we'd restore the incentive to keep inventing—and Mr. Jobs wouldn't be spinning quite so furiously in his grave.

*Editor's Note (10/18/16): This sentence from the print article was edited after it was posted online. The original erroneously attributed the initiation of Apple's litigatory action against Microsoft to Steve Jobs.