Why unit of measure (UoM) is not getting mapped for the scenarios from Ariba B&I and Ariba Sourcing?

As of now, the UoM maintained in the below path in SAP Integration Suite, managed gateway for spend management and SAP Business Network is only supported in SAP Business Network transactions:

1. Sign in to SAP Integration Suite, managed gateway for spend management and SAP Business Network.
2. Click My Configuration > Cross Refs > UoM.

For Ariba B&I and Ariba Sourcing, it isn't supported.

As a workaround, you can use the translation function in the Managed Gateway for Spend&Network mapping tool to apply transformations, refer to this article with screenshots for that: How to use Translation Function in SAP Integration Suite, managed gateway for spend management and SAP Business Network Mapping tool.

Nevertheless, you can share your enhancement request with the SAP Ariba development team through the Customer Influence website. This website is reviewed by our product managers and the ideas with more votes will be implemented in the releases. Your opinions on how we can improve the products that drive your business are critical to our mutual success.

SAP Integration Suite Managed Gateway > Managed Gateway for Sourcing Integration
SAP Integration Suite Managed Gateway > Managed Gateway Foundation & Tools > Managed Gateway for Managed Gateway Portal