I have noticed the same - I think it's simply because people don't know what to say - whether to comfort you, or simply to avoid the subject. I'm not saying I've had the same experience, just that I have observed what you are talking about. People seem to have a similar problem whenever talking to someone who is having a hard time - they can't help but compare - "Oh, well this happened to me which is really quite similar so I know how you feel". I will freely admit that I used to do this, until I noticed it - it's easy to do. I think its the selfishness of human nature (to put it pretentiously); as Sophocles (I think) said, "We see the tragedy, but the tears we weep are for ourselves"; often we cannot see other peoples' tragedy as any different from our own. But I digress, and may well be going off on a tangent into something which is of no interest to anyone. I apologise.
Also, you are not worthless
My condolences.
Take care.