Why do we look after the time limit?

[OmiOmen]

I know that I am not the only person to look at a BFN test after the time limit is up and see a line but why do we do it? I took a test this morning and got a BFN and because I was getting DS sorted I just forgot to throw it away and then I came back upstairs later and saw a faint line. I know it does not mean anything and this is just a little rant about why we punish ourselves.