Comment by pjmlp

Because of the rendering features provided by HTML, CSS and JavaScript semantics.

That is why Flash became so loved by Web designers, allowing them to target a rendering surface, completely bypassing the browser.

Also why we are now having Flash's revenge with WebGL/WebGPU/WebAssembly.

However the "until you have to debug it" still applies, unless you ship the browser with the application, but that isn't something people usually do. /s