What's this hiring pattern about?

Several times within a month or so of job searching, I've experienced the following pattern:

1. Recruiter reaches out via LinkedIn and asks to book a call via a calendar site

2. I book time

3. They ask for a resume, which I provide

4. They cancel the call, usually very close to the scheduled time

On the one hand, I don't really mind this - the whole process takes two minutes of my time, it's a numbers game, etc.

On the other hand, I'm curious about what's happening on the recruiter's end. I assume they've automated steps 1-3, and something about my resume doesn't click. But, my resume and LI profile are nearly identical -- so it seems like their (presumably AI-driven) initial outreach could have screened me out in the first place.

Any insights welcome.