Happens to me a lot. In addition to what is said above, I think it has to do with human greed, envy, etc. -- wanting what you can't have. In the first auction it looks tempting -- maybe something fresh, that you never saw before, that you want and might get cheap, steal it from others, etc. But once it is offered to you, it loses its luster. Like you want what you can't have, but.....

Also: it might help to make a pitch (explanation) when making a second chance offer -- like say this is your only other one (assuming that is true), saying you won't be offering it again (if true), etc. I believe they have a place for making comments like these.
Robt.