This argument is made under the assumption that people want to change their habits while self-isolating. Some people may desire to use self-isolation as a time to relax and practice self-care. People could be already satisfied with their habits and deem themselves healthy, so they won't want to change anything.
While self-isolating, people want an escape rather than another change in their lives. With so much changing in society due to the pandemic, people would rather get lost in fiction. They would find it much more comforting to distract themselves instead of reading more science-related books.