Research data should be archived properly to guarantee that future research can profit from it and to ensure that your research can be reproduced by the scientific community.
Collecting research data is time-consuming, money- and labour-expensive. Therefore, archiving your data is oftentimes cheaper than collecting data anew, especially since sometimes, your once collected data can not be reproduced (for example data on weather).
Archiving your data is recommended by research funding third-parties and scientific publishers to ensure good scientific standards. Sometimes it is even compulsory. Also, there are benefits for you as well.