Why do we believe this concept? It's a business or political decision to delete something after X days/years, not a technical limitation. It's similar to govern

Why do we believe this concept? It's a business or political decision to delete something after X days/years, not a technical limitation. It's similar to government policy about data retention policy for X years. This concept is invented to calm the public, but there's no difference in technical aspect. The servers still keep everything. It's the contrast of the old days, when the mainframe has to discard data because there's no space left, or it's simply too expensive to keep everything.