An ATM for Your Data
An effective data unification system is like having an ATM network for your data.
Instead of having to get to a branch (and only during open hours), wait in line, and talk to a teller, even for simple withdrawals and balance inquiries, with an ATM you can do many common operations on-demand and quickly.
Similarly, instead of having to identify a data source, get to the tools for querying it, perhaps waiting for pre-processing/updates, and often needing to talk to a data teller (engineer/administrator/analyst), with effective data unification you can answer common (whatever you define as common) questions on-demand and quickly.