As a company you're also competing against other companies for hires. Good candidates can get offers from multiple companies. If you're going to tell candidates

As a company you're also competing against other companies for hires. Good candidates can get offers from multiple companies. If you're going to tell candidates to make an opportunity cost sacrifice of several weeks of work just to the the possibility of an offer then you better be offering something extremely valuable to the candidate. Otherwise why would the candidate take the chance on your interview process if they can secure an offer from other companies without paying the opportunity cost? The result is that this interview process will likely only be pursued by candidates not able to get offers from other companies.