Why do some companies advertise job vacancies but don't give us opportunities to interview?

Answer: This is a great question. I do not know what happens in every company that has engaged in this behavior whether intentionally or not. I am only offering my professional perspective on this as I have experienced these concerns from clients. The best way to explain is to give a few scenarios of the most possible circumstance (s) that happen often.

They are:

The company has found an internal candidate.
They were testing to see what candidates were available to them.
The posting may be invalid, (meaning posted in error from an employee in human resource.)
The company forgot to remove the posting.
The company is re-evaluating the position.
The company was not satisfied with the candidate pool.

I hope these common scenarios make sense to you all.

P.S.: If you are applying to opportunities through some of the popular job portals like monster.com, indeed, etc do not apply for jobs that have been posted for 8 days or more. The reason for this is to avoid being #1,000th candidate to apply versus #127th candidate to apply. You want to give yourself a fighting chance among the candidate competitions.

Best Wishes and Success,
Swepps & Associates Team