I suspect that almost everyone on this Board has had that experience. There are many possible explanations including:

- Not receiving the email in the first place (there are ancestry delivery issues including people ending up on 'Do Not Contact' lists without realizing it)

- Not knowing how to share trees and not wanting to admit it

- Taking the DNA test as a favor for someone else

- Not logging in regularly to see results

- Having personal issues that interfere with ancestry work (illness; job loss; moves; etc.)

- Having private things on their tree that preclude sharing (NPEs; adoptions; and so on)

The type of request you send can also make a difference in your response rate. I always share the name of the test they matched, my name, surnames and locations for my family tree. I also suggest that they might share surnames if they are unwilling to open up their entire tree. If there is a surname of interest, I respond by asking for one or two of their ancestors with that surname. I also ask them to look at my Tree. The vast majority of matches do respond and do share.

And, of course, some people find it easier to just ignore emails than to explain why they won't share their Tree.

It can also take a while for responses. Two weeks ago I received a response to an email sent in 2012! Last night I got an answer to one sent in November 2014.