One of the major benefits, if not THE benefit of process orientated approaches to managing your IT services and infrastructure is that it enables continuous improvement.
This means that you are never totally satisfied with the current state of affairs and that you always want to improve your services. I mean, it is the way life is to always set higher standards or aim for higher goals, otherwise life can become a little boring.
The reason why ITIL enables continuous improvement is that it allows you to measure all work that is done. That is why it is so important to record everything. Technical people normally hate it to do documentation and even worse, they hate it to document everything they do, while they have more important stuff to attend to like fixing a critical server. The benefit of having everything recorded outweighs the hassle of recording it by far. Unfortunately it usually takes a while to realise these benefits which make it even more difficult to get the techies recording the stuff. There are of course several positive ways of getting them to do it, but I will not go into all of that right now.
Anyway, now that you have everybody following a strict process and recording everything they do, you can start measuring everything. By measuring it, you can make informed decisions and take actions to improve it. If you don’t measure it, you cannot manage it. If you cannot manage it, you cannot improve it. Not having a process and tool to measure your IT department’s performance, is like an athlete not having a stopwatch to measure how fast he goes around the track. The athlete will not be able to know his weak points where he needs improvement, if he does not measure his performance. He will also not be able to know if his performance improves or degrades over time, without using a stopwatch and recording the times.
If something as simple as running around a track uses a system of measuring and recording to continuously improves, why are so many IT departments not doing the same thing?
Once you have a mature process and are able to measure the output of the process, you can start to apply quality improvement methodologies. A well known methodology is the Deming cycle, which is a continuous circle of planning, doing, checking and acting. First you plane the process that needs to be followed, and then you get the people to follow it (do). When people follow the process you can measure it (check). The measurements will be used to make informed decisions to act upon to ensure continuous improvement.
To conclude, managing IT services without a structured process based approach like ITIL, is like an 800m athlete not knowing how far 800m is and without a stopwatch.