It's because non-depressed people don't understand what it's like to be depressed all the time and lack the ability to empathize. Sometimes there are ones that try to help or understand, but there are also the ones that think our reasons are invalid, therefore they will either make fun of us or get angry at us, but all it does is make us feel worse about ourselves.
I agree, but don't make the mistake of thinking it's just because they don't understand.
I had a lady friend who had been through depression and considered suicide herself.
I spoke to her about how I was feeling, and she just called me negative, implied I am toxic (didn't say it outright) and cut ties with me, citing that she "doesn't need bs in her life" as the reason!
This person has been through it herself, and is also a paramedic!
On many levels she should know better.
The trouble with her is that her 'recovery journey' has turned into pretending that everything is honey and rainbows.
She's turned into the kind of person that uploads things like "happiness comes from within" on social media.
So she doesn't see the world as it is, and pushes away anything that seems to contradict her internal flowers and bunnies narrative.