Has anyone else noticed Threads is completely absent from AI-generated search results?

I've been using ChatGPT, Gemini, Claude, and Grok regularly for research and I keep noticing the same pattern with which social platforms actually show up in results:

• Reddit — almost always cited or surfaced
• LinkedIn — comes up frequently, especially for professional/business topics
• Facebook/Instagram — occasional
• Threads — never. In months of use, not once.

(X/Twitter is a special case since Grok has exclusive access, so I'd separate that out.)

My question is whether anyone has insight into why Threads is so absent. A few theories I've been sitting with:

1. Crawl coverage — Reddit has been publicly indexed for a long time. Threads is newer and Meta may not have the same open crawl access.
2. Training data — AI models are trained on historical data. Threads launched in 2023 and just may not have the same representation.
3. Data partnerships — Reddit notably signed data deals with AI companies. Has Threads?
4. Content structure — Reddit threads are highly structured conversations that translate well to retrieval. Threads content may not have that same signal density yet.

From a marketing standpoint this feels important: if AI search is increasingly where people discover information, a platform being absent from those results is a real discoverability gap.

Has anyone noticed this, and are you factoring it into where you recommend clients post?