Before we had kids, we never unpacked. My husband and I each had our own suitcase, and it was pretty easy to manage without unpacking.
But with kids, I have to unpack or I would waste too much time trying to locate things. I have one very large suitcase that I pack my stuff in as well as my kids things. I assign each kid and myself a drawer, assign another drawer for things like hats and sunglasses, and so on. Makes it much easier for everyone to get ready in the morning and to get ready for bed each night, because they know exactly where each item they need is located.
Also, I find that packing to go home is much easier if I have unpacked. If I didn't unpack, I'd have to dump it all out anyway because in order to get it all to fit I have to roll the clothes, arrange the larger items a certain way, etc...it is like putting a puzzle together!
My husband, however, still lives out of his suitcase on our trips because he has a smaller one that only contains his belongings.