It’s just different use cases. A tree would show relations to the individual, a line just proves they descended from a particular person. Applications of it might be a bit outdated, but I don’t think there is any more reason to show relations in a tree than “oh, that’s neat”.
I suppose it is in a fashion, but not necessarily. Let’s say you know you have a ancestor that was part of the first expedition to the arctic. The line of ancestor to descendent between that person and you would be the bloodline. Everyone you are related to would be your family tree, but that could be hundreds of people depending on how far back you go, and could be thousands of people if you start looking at everyone descended from that person. But you are only concerned with the direct line of lineage between them and you, and that would be your bloodline.
It would generally be between a person and a specific ancestors of theirs, so that depends on who is is tracking towards. Often it will be qualified with something like “Paternal Bloodline” or such, in which case it would follow the father, the father’s father, the father’s father’s father, etc. Or for royalty, it would track from some historical sovereign figure and follow their legitimate heirs down to the individual being examined.
I don’t even bother going that far. I just have a [words]receipts@[domain].com and use it for all of those e-receipts, accounts that make you sign up at checkout, known spam generators.
If I need to search for a receipt for any reason, I have it there. But none of it clogs up my real email