Squeak,
No, they don’t need to be sure it will work, but some of these ideas are just so out there. For example the guy that I saw hit his mother, and the one who is more than 30 years older than I am. If I was being unreasonable or if there was a reason why I should reconsider my “no” answer, that’s fine. But when I get this type of call, I can tell that there’s no reason why she’s setting up him with me other than the fact that we are both single. It tells me that no thought at all was put into this. Many shadchanim will tell you to just go on one date. But there is such an emotional (and often financial) investment that goes into this. And the more time you end up going out only one time, the more frustrating and difficult it all becomes. If there’s no chance that it will go anywhere (such as with the two cases I mentioned, but there have been others as well), what is the purpose?