Myself and DSIS disagree on this.
I think if you're sending presents to family members (we only send to close family, think parents, sibling and two niece/nephews), you should wrap them before posting.
The past couple of years my sister (and now my Mum) have gotten in the habit of sending presents for mine and my daughter's birthday and Christmas direct from the retailer unwrapped and often with receipt. It's then on me to wrap and put under tree or hand out on birthday with a tag saying from Aunty X.
Keep me honest here, am I being unreasonable for finding this a bit impersonal? I'm grateful for the gift for me and DCs, and DSIS says it saves on postage but I find it a bit naff to open an Amazon box with a preloved book and a receipt. I never know when they're coming & we also order from Amazon to intercept & wrap the box.
YABU - sending direct and expecting recipient to wrap and dole out is fine.
YANBU - it's impersonal