Had two phone interviews with the recruiting manager and hiring manager. they said will call me for an onsite interview but did not receive any calls later

The interview process is fairly easy, starts with a phone interview and proceeds to an in person interview. Although I didn't receive an offer what I have noticed with this company is that they will post positions, collect alot of resumes and conduct alot of interviews and yet don't fill the position as it seems to be posted again and again. It makes me wonder if they already have an internal candidate in mind to fill the position but are obligated to post the position to external candidates knowing it will be filled by the internal candidate.