Virtually every single time I pick up my shotgun or one of my pistols to dry-run in my house at night, I can very easily identify targets/target areas yet only see the sites due to the tritium.
I have also shot outside at night where I could identify the target but would not be able to easily see sites that were not their own light source.
Sure, there are times it's too dark to ID a target without a light source. Sure, there are times it's kinda dark and you could see a fiber optic site.
But there are tons of times you can ID the target and the tritium lets you see your sites (or lets you pick them up more quickly)
The only thing necessary for evil to triumph is for good men to do nothing.