It’s practical for a lot of reasons. DNA takes 1000s of years to degrade vs digital devices which constantly have to be replaced every few decades.

It is multithreaded, DNA can be read at any entry point in parallel along the strand.

It’s cheap: every living thing on earth can store DNA, it’s dirt cheap.

It’s compact and dense.

It can be expanded past base 4 to any arbitrary base with synthetic nucleotides.

https://news.microsoft.com/innovation-stories/hello-data-dna-storage/