Questions for recruiters: Why does it take some recruiters MONTHS to get back to you?

I understand that if you are getting a lot of applicants it can be difficult to get through all of them and time consuming. But why would you even post a job listing if you don't plan on contacting them at all until 6 weeks - 4 months later? I would get it if you already interviewed them and said "this job won't start for four months" that's fine. But after submitting your resume or having your first interview and then hearing "we would like to offer you the job!" months later is super irritating and a bit rude to be honest. But once again, idk the recruiting process so idk if they realize how rude it comes off.

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