More like you accidentally didn't give [transfer] them a house [land], because you didn't actually own the land in the first place.
Your ownership claim descends from the chain of previous owners. It's possible that there are encumbrances that aren't currently known. A common example is "paper streets" where a neighborhood was planned out but never built. Then all your neighbors might have an argument that they were looking forward to that right of way that was supposed to run through what is now your plot. It's a huge uphill legal battle on their part, but the point is it's possible they could make it. As more old records are digitized, things like this pop up.
It's not a great system, but like most things in the US, that's just the way it is (in most areas).