I've never really had any issue with my skin as far as acne, blemishes, etc.. I've always had good skin thanks to a tight skin care routine. Always taking off my makeup at night, moisturizing, using sunblock and spf, etc..etc... I've always gotten compliments on my skin. People usually ask if I'm wearing foundation, bronzer, or powder, even when I'm not.
I tend not to skip using foundation often. I have used it for years upon years. I think that foundation can give your skin an extra layer of protection from harmful elemental factors and it gives you such a pretty and finished appearance as well.
We are all extremely different as you can tell by the responses! I don't "need" foundation, but I choose to wear it.