This isn't _entirely_ unique to the tech sector, although the fundamental nature of software does make it a little different...
I mean, let's step away from tech for a second and talk about, I don't know, fast food, for example. Why does everybody have a drive-through window? Because whoever introduced it first, was making a lot of money from it. Why do they all offer meal-deal options on their menu, where you get a main dish and a side dish and a beverage for one price? It was a money maker for whoever introduced it first, and everyone copied it. Why do nearly all pizza chains deliver? Same reason. When your direct competitor introduces something that's wildly popular and makes a ton of money, you do something like that too, in order to stay competitive. That's the nature of business, and it's *mostly* a good thing, most of the time.
There's a reason you can't copyright ideas, only specific expressions thereof.
With all of that said, I said the nature of software does make it a little different, and what I mean is this: the cost of implementing a software feature is the same whether you're rolling it out to fifty users or fifty million users, so you spend the same amount, but you get more benefit if you're larger. This does somewhat amplify the advantages of being a large company.
But yeah, all businesses that are any good at business, copy their competitors' best ideas. Otherwise they eventually go out of business. Why did Sears, once a quite major company, shrivel and die? Because they were badly run and didn't keep up. Amazon exists, and you think people are going to wait for your *quarterly* catalog to arrive in the mail, and order from that? Sorry, no, you lose. (It isn't just Amazon, of course. Their brick and mortar business could have survived the arrival of online ordering, but then they would have had to figure out how to compete with Wal-Mart and Target. They didn't.)