Modeling is a key tool for business analysts.
A picture is worth a thousand words. If a requirement is written in 20 words, a picture will be equivalent to 50 requirements.
The model can show a complete picture of a set of requirements allowing the business analyst to evaluate the complete picture.
It is far easier to understand a database by looking at an ERD than it is looking at the table definitions.
It is easier to understand the complexity of a process by studying a process model than it is by reading the job steps of each stakeholder.
Models are just another language for understanding the domain a business analyst is implementing a change in. Like any language practice and experience make us better are reading the language.
Even if models are not required, taking the time to understand things through models gives us a deeper understanding.