User onboarding surveys - why everyone ignores them?

I needed an onboarding survey for my SaaS, so I started researching what other products ask during onboarding. I saw many products don’t have any onboarding surveys at all. Surveys seem crucial for understanding users better, so why aren’t they more widely implemented? Are product teams overlooking this, or are there challenges I’m not aware of that prevent them from using onboarding surveys?