1Focus offers basic app and website blocking for free, forever. The 14-day free trial is for the optional 1Focus Pro, which adds extra features.
1Focus Pro requires continuous maintenance beyond updates, upgrades, and support. The website lists behind the website categories have to be maintained and updated with user suggestions.
A one-time purchase would only be sustainable if we limited updates and support. We would have to hold improvements back for paid upgrades, and you would end up with an outdated, unmaintained app and no support eventually.
The subscription model makes the development process more efficient. We can invest all our effort into a single, up-to-date version with continuous maintenance, updates, upgrades, and support.