The main purpose of the utilization era will be to support space-based scientific research and develop technologies for human exploration Beyond Earth Orbit (BEO).
Now that the US Segment of the ISS is completed (bar the addition of potential future modules such as a Bigelow inflatable), the ISS has extraordinary capabilities to conduct research in space, the likes of which have never been seen before.
Due to its huge solar arrays and Ku-band antennas, the ISS has power and data capabilities which are capable of supporting multiple payloads, while also providing them with a long-term, stable platform on which to attach.
The benefits of this is that scientific payloads can be attached to the ISS without needing their own power supply, data downlink capability, and attitude control system, thus significantly reducing the cost and time required to fly an experiment in space.
via Tech Demos: NASA preparing for full ISS utilization in post-Shuttle era | NASASpaceFlight.com
The Committee to Nuke Elysium 