Organizations who start out on an IT self-service initiative with a focus on reducing IT costs usually find that costs go up.
Because when a self-service portal is built to reduce transaction costs for IT, it isn't built to optimize the experience for the IT customer. And if the IT customer doesn't get an experience that is better and faster than calling or emailing the service desk, they will continue to call or email the service desk. Costs go up because the service desk is still fielding the same number of calls, and you've spent time and money building a self-service portal that nobody is using.
In a nutshell: Managing from a pure cost perspective, increases costs.
The Return on Investment (ROI) of a self-service portal—like any other digital technology—relies on adoption. People need to use it, or the intended benefits will never materialize:
Volume of calls to the service desk remain high
IT remains in fire-fighting mode
IT people have no time to pursue transformative service improvement and automation projects
For a self-service portal to succeed, it is absolutely critical to focus on value (an ITIL 4 principle), not cost. The value proposition for the IT customer should be clear: Get what you need here, faster than waiting in a call queue. If your self-service portal can't deliver on that promise IT customers may try it out, but it won't enjoy the sustained adoption that you're looking for.
A self-service portal needs to be the line of least resistance for a user. It needs to be low effort. Frictionless. If they hit a friction point that is preventing them from getting the help they need, they will quickly resort to default behavior—calling the service desk—and the value of the self-service channel is lost.
This is why it is so important to work with your end user community to understand their needs and expectations; to co-create (another ITIL 4 concept) a portal which balances out value for the IT customer against efficiencies for IT operations.
If you offer them something you know they want (because you've asked them what they want) they will use it—and self-divert traffic from your phone and email channels to web and mobile channels.