There is no direct record of Proto-Indo-European and there's barely any non-hypothetical evidence of Proto-Indo-Europeans. Why is Indo-European considered a language family while Ural-Altaic isn't, when the latter makes more sense nearly in every way?
For Indogermanic, there are ample word correspondences and regular sound laws allowing the reconstruction of a proto-language (at two levels, one before and one after the split of the Anatolic branch including Hittite). There is no doubt that the known branches all belong to one language family.
For Ural-Altaic (proposed in very different shapes comprising more or less branches) no convincing sound correspondences and sound laws have been found up to the present day. That the languages are typologically similar is not enough to demonstrate a language family.