Because security questions are an additional attack vector and should not be used at all. The dev-time is better invested in enforcement and encouragement of long & secure passwords and 2FA.
What would be your workflow for password reset? That is the typical use case for security questions.
Enter E-Mail -> Receive Reset-Link
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.