Importing data is intended to supplement data tracked via Salesforce Audience Studio default tracking mechanisms. It is not intended to replace Audience Studio tracking mechanisms entirely. Therefore customers will experience a degradation in service by choosing to only import data.
Additionally, in order to import data, the file must contain a unique id for a user for each record in the file - either the Audience Studio unique id for the user or the customer's unique id that has been mapped to the Audience Studio user via User Matching.
Some of the core reasons to use Audience Studio are to manage Identity and centralize user-level data for advertising and content personalization. Additionally, the Audience Studio includes insights that help inform targeting and personalization use cases as well as campaign and personalization optimization.
Even when importing data, user matching is still required. Is it possible to gain insights and make data actionable by importing data? Yes, it is, but there are inherent delays and all real-time use cases, such as real-time site personalization, real-time suppression, and real-time retargeting are no longer supported. Additionally, many default reports and attribute enrichment features rely on Audience Studio tracking to be implemented.
Why limit the opportunities when default tracking is optimized for performance and provides a full featured platform experience? The opportunity costs are high with import only and the reality is that the full value of using the product will never be realized using an import only approach.
To better understand Identity, see the following related articles.
Which import options are available to me?
See more details and options in Implementation > Data Imports and Exports