As a young HR professional myself (23) I have found it challenging to gain some of the respect our field deserves. I believe it may be partly due to my age and the weight a position in HR carries. I started at age 20 and have found people hesitant to trust someone so young. In combination with this, I also feel through my experience at two different companies so far that HR departments are widely undervalued. My previous supervisor made this statement to me a few times, but I never fully understood it until I left back in October and took on my current position as a 1 person HR department for a company with 180 employees.
Hope this helps!