When you have 70+% browser market share, stopping support for something _is_ killing it.
What they can do is remove support for XSLT in Chrome and thus basically kill XSLT for websites. Which until now I didn't even know was supported and used.
XSLT can be used in many other areas as well, e.g. for XSL-FO [2]
[1] https://www.w3.org/TR/xslt-30/ [2] https://en.wikipedia.org/wiki/XSL_Formatting_Objects
Browser can render XHTML which is also a valid XML.
So it's pretty natural to use XSLT to convert XML into XHTML which is rendered by browser. Of course you can do it on the server side, but client side support enables some interesting use-cases.