[beetwenty]

Std::string half of all allocations in the Chrome browser process (2014) [0]

The key difference is that web browsers support a highly arbitrary and mutable dataset. A game engine's assets exist in a mostly-static space. The things that are allocated at runtime are things that should have a known maximum, because going over that maximum will start to overrun latency targets. Many assets are streamed, but still hit a certain size and bandwidth budget, and so are still "basically static" - some degree of compilation and configuration at runtime always takes place for rendering features. The genuinely mutable part of game state while playing is in a comparatively confined space, and that allows a lot to be pushed to build time, where it's easier to validate and to maintain.

The features that change this picture are editors and arbitrary data imports. Web browsers are all about these two things. When you click a link the document may load thousands of gigantic images, and I might try to copy-paste the entire contents of Wikipedia into a text box. The engineering requirements are much broader as a consequence, and there are more rationales to need genuine "black box" interfaces supporting a complex protocol, as opposed to a static "calling function switches on a specified enum" approach, which is sufficient for almost every dynamic behavior encountered in game engines.

[0] https://news.ycombinator.com/item?id=8704318