Azure Multi-Factor Authentication is being used for custom applications and as a way to help secure them. Security is in the forefront of most applications that are external or user facing. Multi-factor authentication is widely considered a very strong standard to secure an application and verify the identity of a user. Azure Multi-Factor Authentication makes this easy to implement and manage.
- Ease of use
- Industry standard
- It can be difficult to work with when deviating off the standard use cases
If your solution falls within their standard use case or you have Office 365 - then it makes total sense. If you need a lot of customization or have a really specific business process that causes you to deviate from the standard flow it usually makes more sense to create a custom solution.