Some data are extremely precious and should never be lost. These could be legal, health, or financial documents. Alternatively, they could be letters, photos, or videos of personal value. These data should be kept by you, not forgotten on a drive or managed by 'the cloud'. DNA can last for generations.
The world is generating more data than it can store. Demand for storage will soon outstrip the availability of memory-grade silicon being mined. Together with slowing density advances from the storage industry, a new medium is need. DNA is the densest, replicable storage medium known.