Ask HN: What happened to Greasemonkey?

Its seems an addon that was very much ubiquitous has completely lost its presence in the browser world. There are so many things where greasemonkey scripts can be a perfect solution, like filtering HN links with specific keywords, or redirecting quora urls to "?share=1", or any nit-pick change that doesn't necessitates a separate addon. Why aren't userscripts used anymore?