Why do scholars disagree about the Indo-Hittite hypothesis?

The Indo-Hittite hypothesis is a subject of ongoing scholarly debate regarding the classification of the Anatolian languages within the Indo-European family.12

The disagreement stems from the fact that Anatolian languages, such as Hittite, lack several grammatical features common to other archaic Indo-European languages, including feminine gender, subjunctive and optative moods, and specific verb tenses like the aorist and perfect.2

Scholars have proposed two primary interpretations for these differences:

• The Indo-Hittite Hypothesis: Proponents argue that Anatolian and Proto-Indo-European are collateral descendants of an earlier, reconstructed stage called "Indo-Hittite." In this view, the absence of certain features in Anatolian is explained by its direct descent from this more primitive linguistic stage.12
• The Traditional View: Other scholars maintain that Anatolian is simply a branch of Indo-European that inherited but subsequently lost these grammatical categories.12

Currently, no scholarly consensus exists, as extreme versions of both models are considered unlikely. Emerging evidence suggests that some of these categories may be reflected in Anatolian in ways that differ from traditional reconstructions, indicating a complex evolutionary history.2