I dont think its absolutely necessary but I honestly thinks it helped in my interview process. I had terrible grades but during my interview they really dug into my experiences and asked me a lot of questions pertaining to them. Working as an aide shaped my beliefs and how I want my style of treatment to be.
My Stats:
Overall GPA: 2.76
Pre-Req GPA:2.93
GRE: 149V, 151M, 3.5 W
Volunteer/Work experience:
PT Aide @ outpatient clinic: 1 year, 500~ hours
Rehab Tech @ Morristown Medical Center: 3 years, 2500~ hours (I honestly think this is what helped me a ton)
Not only did working in the hospital expose me to the acute side of PT, but it showed how to work in an interdisciplinary setting with nursing, OTs, speech, etc.