BluePi Senior Java Developer interview questions

it was 2 round of F2F interview. I have cleared all the rounds and they declared that I have cleared all the round. The final round was HR round where they told me about their company. but I did not get offer letter after all. When they are not taking the people then why they schedule the interview and wasting the candidates' time. I have message the HR of the company in LinkedIn but they did not reply after all.