[jodrellblank]

They would have multiple codebases to maintain then.

I think they were the IE engine for the main explorer folder view in Windows 98 - all the active desktop and custom folder backgrounds and theming the sidebar which slowly vanished in XP and onwards was MS-HTML and CSS based.

It wasn't a stupid design decision, it was just a design decision.

[rythie]

They wouldn't really need to maintain the OS stuff, the HTML is not changing for it really.

In contrast the HTML on the web is changing very quickly and therefore the browser needs frequent updates to keep up.