Because it is simply broken and there is currently no workaround.
According to change the length :
"Previously, ngInclude only updated its content, after this change ngInclude will recreate itself every time new content is added. This ensures that there is always one rootElement for all contained content, which greatly simplifies the definition of CSS styles for animations."
but instead of being improved, he seems to have been broken.
According to the comments here, the current implementation is broken.
Other sources will tell you the same thing.
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