Propeller Consultant - Project Lead interview questions

I had great conversations with my interviewers - the initial one being a phone screening, followed by a skills interview and a cultural fit interview. My third interview was 30 days after my initial phone screening, and I felt it went well, but never heard back. I sent a follow up email to the HR contact 2.5 weeks following my last interview, and still have not heard back (it's now been just shy of 4 weeks since the interview date). Obviously I assume I am not moving forward in the process, however, for a company that prides itself on excellence and the caliber of it's employees, I'd expect the courtesy of at least a declination notice. I am disappointed, but I honestly expected more professionalism after moving that far through the interview process.