为什么 Internet Explorer 不支持 SVG SMIL 动画
Why is SVG SMIL animation not supported by Internet Explorer
Internet Explorer 选择不支持 SMIL 动画是否有原因？ Internet Explorer 的未来版本是否支持 SMIL 动画？
根据您链接到的 caniuse.com 页面和 official status page for IE and Edge, Microsoft is not planning to add SMIL to IE or Edge anytime soon. Actually, even if it came to Edge it would probably still not come to IE since IE's primary purpose in Windows 10 is legacy compatibility. As for why, I don't know for sure. This (old) answer 表明微软对该规范有一些反对意见，但因为那是 5 年前的事，可能不再是这种情况了。
Microsoft believes that there are spec issues to work out before they add SMIL
此外，this IE blog post 他们在 IE 9 中实现 SVG 时解释了他们当时不支持 SMIL 的原因：
[...] support for SMIL animation of SVG in the web development community is far from strong. The leader of the SVG standardization effort wrote that not supporting SMIL in its current state is probably best “since the SVG WG intends to coordinate with the CSS WG to make some changes to animation and to extend filters.” There’s already work started to reconcile CSS3 animations and SVG.
这听起来像是他们期待规范发生变化，并且希望在实施之前稳定下来。这样一来，他们就不会因为交付过时的实现而陷入困境。也许到现在为止，该规范已经足够稳定，可以实施，但不再值得为此付出努力。
Internet Explorer 选择不支持 SMIL 动画是否有原因？ Internet Explorer 的未来版本是否支持 SMIL 动画？
根据您链接到的 caniuse.com 页面和 official status page for IE and Edge, Microsoft is not planning to add SMIL to IE or Edge anytime soon. Actually, even if it came to Edge it would probably still not come to IE since IE's primary purpose in Windows 10 is legacy compatibility. As for why, I don't know for sure. This (old) answer 表明微软对该规范有一些反对意见，但因为那是 5 年前的事，可能不再是这种情况了。
Microsoft believes that there are spec issues to work out before they add SMIL
此外，this IE blog post 他们在 IE 9 中实现 SVG 时解释了他们当时不支持 SMIL 的原因：
[...] support for SMIL animation of SVG in the web development community is far from strong. The leader of the SVG standardization effort wrote that not supporting SMIL in its current state is probably best “since the SVG WG intends to coordinate with the CSS WG to make some changes to animation and to extend filters.” There’s already work started to reconcile CSS3 animations and SVG.
这听起来像是他们期待规范发生变化，并且希望在实施之前稳定下来。这样一来，他们就不会因为交付过时的实现而陷入困境。也许到现在为止，该规范已经足够稳定，可以实施，但不再值得为此付出努力。