Why do credit scores differ between credit bureaus?

There are three major credit reporting bureaus (Equifax, Experian, and Transunion) and two main scoring models (FICO or VantageScore) which determine credit scores.  Financial institutions use different bureaus, as well as their own scoring models. Over 200 factors of a credit report may be taken into account when calculating a scare and each model may weigh credit factors differently, so no two scoring models are identical.