General Discussion

If your next of kin can't be found, or died/was incapacitated in the same accident, your organs can't be donated because of the inability to know you're wished.

Even if they can be found, some organs are time-sensitive, so if finding your next of kin takes time. Some organs may not longer be useable.

Your next of kin may not even be asked, based on your presumed refusal to consent.

Finally, depending on your spouse, they may be too emotional to consent. I am on my mom's living will, because she is very clear she's doesn't want to be kept alive on machines - and she wants to make sure someone will authorize them to remove the machines. She knows my father may week be unable to do that.