Simply amplifying all frequencies (low, mid and high sounds) would not help you follow conversations, and would make everything equally loud. Therefore, a hearing device should amplify some frequencies a bit more than others.
To make things complicated, your ears may struggle with some frequencies more than with others. This means that the hearing device must also compensate for this loss. By creating a profile, the hearing device will be optimized to you.
The profile is calculated with a formula based on the results of both the personalization results and your age and gender. This algorithm has been developed by the National Acoustic Laboratories (NAL) and is designed to make human speech as clear as possible.
So in short, the personalization will help make following conversations easier. It will still take some time to get used to wearing a hearing device.