How to tell the shadchan that you do not want to pursue the suggestion? Again, there are several things to consider.
You don’t have to say much – if you don’t want to. You can simply say, “We’ve heard nice things. We simply don’t think it is shayach.” Or “We’ve heard wonderful things, we don’t think it is a good fit.” You don’t have to explain further. At best, do not use the phrase, “I just don’t see it.”
If you are working with a shadchan who has been looking out for shiduch ideas, it would be helpful to give an explanation of why you think it is not shayach. In this way, you can help them narrow their criteria; make it easier for them to help you. “My daughter really wants someone who loves to be around people and have friends over.”, “My son needs someone who is strong and independent and can take care of the family when he is away on business.”
Another reason why it is important to share with the shadchan: Perhaps there is something that you found out that she didn’t know about the person. If you share that information, it will make her work easier. She will not be suggesting that person to people who are not shayach. “We understood from you that he was still learning full time, we heard that he is working full time and barely has a shiur once a week.”
Lastly, sometimes, you might hear things that are not accurate. If you mention what you have heard to the shadchan, she can help clarify misunderstandings.
So why is it that people don’t share the reasons? Sometimes, it is that the shadchan will minimize or dismiss those concerns. So they’d just rather not share anything. In that case, you can simply tell the shadchan, “I really appreciate your insights. Nonetheless, this isn’t something we want to pursue or discuss at this point. Thank you.” Others may not share because they fear the shadchan will think less of them and prefer not to share. “We can’t get past her way of dressing.” Or they don’t think the shadchan will understand the rationale. “I can’t get my son to go out with her because he disliked her brother in camp 7 years ago.” Or they simply have a gut feeling that just can’t be explained.
It depends on the shadchan. Is it a random person, or someone who really is trying to help you find shiduch?
Your personality. How forthcoming you generally are.
What the reason is.
If you feel confident / trust the shadchan won’t share the negatives that you say, for example, "I don't like the family".