Comment by PetitPrince

On the other hand blood samples degrade over time depending on how you store it. This makes DNA sequencing more difficult and/or impossible. Presumably the ROI (in a non-dystopian society) of storing those sample long-term doesn't make sense, especially if the primary usecase is screening for diseases (a random PDF from the Association of Public Health Laboratories says biomonitoring/biothreat samples are stored 1 year https://www.aphl.org/AboutAPHL/publications/Documents/ID_Spe... ).

So yes a collection of blood sample is technically also a collection of DNA sequences, but it has an expiry date (a short one compared to the lifespan of an individual!) contrary to a DNA sequence that's pure data.