Knowingly passing diseases/conditions to children

Sometimes people find out about genetic conditions and diseases after they already had children and it’s unfortunate but you can’t blame anyone for it

However; I know a number of people who have always known about something they have, but went ahead and had children anyway, and I can’t wrap my head around it

I know someone with Trisomy 21 who had 3 children knowing this. 2 of them have it

I know someone who struggled with muscular dystrophy since they were a teen and had a child who is now also struggling

I know someone with MS who struggled since they were a teen and had 2 children who also now struggle with MS

Anddddd I know someone who lost a family member to Cystic Fibrosis, had a child who carries the gene, and then had 2 more children knowing this

I don’t know why people do this. They justify it saying “oh there was like a 2% chance of passing it on” or something

The other half of people I know say things like “I have migraines/depression/anxiety/adhd there’s no way I’m risking passing that on to a kid”. Im one of those people, I just have a lot of trouble understanding how someone suffers and struggles with a physical ailment so young (especially one that could end their life early) and then think “well there’s a chance I won’t pass it to my kids so why not?”

Also, feel free to educate me! There’s probably a lot of conditions that are considered less serious because it’s unlikely to be passed on