Rent payments are used to formulate your FICO 9. Your rental tradeline is also used in different scoring models, such as Vantage, and can be used to make credit decisions for lenders who look at more than just your credit score.
Keep in mind that the three major credit reporting bureaus collect data about your financial history to compile a credit report. The data from these credit reports make up your credit score, but each bureau might have slightly different data. So, there can be at least three different FICO scores, since the data at each bureau may differ.
This is why RentTrack reports to all three credit bureaus. You never know what scores lenders will be looking at, so having the most important bureaus covered is key.