They may not understand it, or they might not want to accept that it is something serious. Like IRL45 said, people do joke about things that are uncomfortable. Joking can be a way to say something without really saying it. Any joke consists of raising the level of discomfort into a slightly uncomfortable range and then releasing it. If it is successful, you find it funny. When you don't find a joke funny either it failed to get the level of discomfort right (too high or too low) or it failed to release the discomfort, leaving you still feeling uncomfortable. I'm guessing that the suicide jokes don't really make anybody laugh. Too uncomfortable for most people.

My landlady made some comments about suicide the other day. She was trying to say that she wouldn't be good at my crisis worker job because if someone is suicidal she just says "get over it" or she would suggest methods that the person might not have thought of. She refuses to take emotions seriously and she owns that she just isn't an emotional person. It really comes down to that she isn't comfortable with emotions or an emotional crisis and she doesn't want to try. Part of it is generational. She is 71 years old. Her generation didn't deal with emotions. They hid them and tried to get rid of them. I understand, but I still find her attitude offensive and hurtful, especially since she knows that depression and suicide are personal issues for me. If I try to talk to her she cuts it short and says that's the last that she will talk about that with me "for a long time." I haven't been trying to talk to her and I was not the one who brought up the topic. I confronted her on that attitude and sent her some information on appropriate ways to talk to someone who is suicidal but I don't think she read the information. She agreed to avoid the topic with me, but didn't apologize and told me that she refuses to change her attitude.