Once the excitement of a new device wears off, what keeps owners reading is how little the Basic asks of them: it slips into a pocket or bag, it does not compete with phone battery for attention, and several owners describe using it on commutes or during breaks specifically because it is easy to grab and put away. The small size that seemed like a limitation at first becomes, for more than one owner, the reason they stop reaching for a bigger reader at all.
What owners adjust to is the tradeoff behind that portability: no backlight, a smaller screen than the Paperwhite, and text-heavy formats like manga that some found harder to read comfortably on it. A few owners who started on the Basic ended up moving to a Paperwhite or another device once they wanted more screen for dense pages, but for straightforward reading, the size and portability keep winning owners over even years in.