This has been the trend for many years now, especially with the bigger technology companies. And not just testers, but roles such as software developer in test have been on the downside. Microsoft, Google, etc. all done it already long ago.
Many good points have been made on how the industry has changed and “testing” needs to change with it. Now you have more continous integration, continous delivery, no more waterfall processes. Easy to deliver fixes quickly, and rather the goal should be to try, fail, learn fast.
Of course you still need some “testing” in this world still, but it needs to take a different shape. More integrated into this whole workflow.
This is the case especially with internet software, mobile software, etc. More traditional industries will still go with the traditional roles much longer. You aren’t going to update your car software every day. And if your car crashes due to software bugs, that is a rather big issue. And those industries are much more traditional in other ways as well.
Within the software industry you will likely find similar silos as well. Perhaps in specific projects such as operating systems and platforms, where fast iteration and delivery can be more challenging, large and complex configurations exist, and issues can be expensive.
Personally, I try to evolve my skills into different directions, but building on the existing knowledge and skill (testing and otherwise).