should i eat protien after my cardio workouts?

Hi everyone! I try to workout 6 days a week and I alternate strength training and cardio workouts every other day. On Strength training days I lift weights and take a body sculpting class and after each workout I have a whey protein shake or have a protein bar or something. On my cardio days I do activities such as running, eliptical, cycling, etc. My question is..Should I still drink my protein shake or have a protein bar on the days I only do cardio? I have not been doing this because I thought protein was only good for after lifting or strength training but now I am questioning it as I have read a couple different articles online saying I should still have my protein.