I think people don't understand the suicidal piece and how active it can become so quickly and how it can be so overpowering where it becomes a rational thought.
the reality is, this is just too much for many people.
I wanted to say welcome, and also expand on these points a bit.
The people in your life - whether they are ones you'd consider close, or not - don't have the training to respond to suicidal thoughts, nor do they have the training or experience to respond to pervasive depression. It's hard, and often leads to feeling sad, because sometimes when one is very low - low enough to be looking for a way out of life - those are inevitably moments that go right along with feeling deeply alone and isolated, and believing that there isn't anyone to talk to. This is just one of the many terrible ironies of mental health.
The good news is, though, you can absolutely reach out - as
@BuckarooBanzai rightly suggests, you'll only want to avoid the 'why'. I find the easiest way to do that is to ask myself what I'd like from the support. Do I want distraction, do I want to get engaged in something else...get out of the house...I try and get specific with myself.
Sometimes, your inner answer will be 'I want to talk to someone about what I'm feeling'. Those times are good for reaching out to a hotline, a chatline - anywhere where you'll get connected to someone with rudimentary knowledge about how to talk to a person struggling with being in dark places.
It's great that you are proactive, and your take-away doesn't need to be that reaching out is bad. It's only important to understand that regular, non-mental health folks aren't able to deal directly with the ideation.