Preservation is important for long-term ethical communication of your research. This includes sharing your data and ensuring that data is continually accessible long after you have finished and published your research. This is often a prerequisite to funding and publishing, as it is required by major funding agencies, both government and philanthropic, as well as many journal publishers. Typically sharing your data means depositing your data into a repository, and ideally it would be unencrypted, uncompressed, and in a commonly used open file format.
Established repositories allow for easier sharing and maintenance of data, often having built-in mechanisms to maintain data integrity along with metrics for researchers to monitor reuse of their data. They further help with discoverability, particularly through issuing permanent identifier links like Digital Object Identifiers (DOIs) which are often included in journal citations. Specialized data repositories also exist for protected data, where researchers can privately and securely store sensitive data as well as control access to it.