It is true that very occasionally features are removed from the web platform. It is also true that the incentive structures that exist hugely favour not removing features or otherwise breaking existing content. For a feature to be removed there needs to either be an incredibly compelling reason (e.g. a security problem), preferably so obvious and widely agreed on that vendors are able to make simultaneous releases containing the change in order to mitigate the effect on the competitive landscape, or there needs to be a negligible measured usage of the feature. The latter is most usually the case when the feature was never widely implemented in the first place e.g. some (but not all) vendor extensions.

If it were easy to remove unpleasant features from the platform, browser vendors would be the first people clamouring to make it happen. For example, off the top of my head, there is widespread agreement that it would be good to get rid of, or otherwise improve in backwards-incompatible ways:

* Sync XHR * document.open * document.write * AppCache * localStorage

But that can't happen, because the desire of browser implementors to simplify their implementation is less important than the need to keep sites running. Apart from anything else, as stated uptrehad, breaking sites is a sure and certain way to get people to switch to a different browser.

Yes, but security is also the only reason users would accept losing access to certain websites - and then only grudgingly!

Tell a regular browser user they will lose access to their favorite website forever because JavaScript developers prefer writing "flatten" to "flat".