alt Hacker NewsThe framing of "a professional game developer.. job is to ship a product" is very indie. Places like ID, Bethesda, Volition (RIP) etc.: like a hundred people worked on the product and many did not own shipping the product. When you have tech team of 10 - 30 people whether you should make your own engine was more of a question. Lots of very popular games are made on their own tech.
Also, like what do you mean by engine? Minecraft was made with LWJGL.
And Minecraft physics are limited to AABBs and rendering was flat unlit quads until quite recently. But they definitely couldn't have done the infinite cube world easily on Unity or Unreal, so in that sense it was necessary to build their own.