It seems they are relying on the developers to offer free "lite" versions of their applications in order to provide a "trial period" sort of thing. And I suspe

It seems they are relying on the developers to offer free "lite" versions of their applications in order to provide a "trial period" sort of thing. And I suspect this might be better overall for the developers. Consider, if you released an application that someone might plausibly only want to use for 30 days or less, and then have no more use for it. If Apple forced all non-free applications to have a 30-day trial period, then you may be losing out on many sales from people who only need your program for a short time. (E.g., a city travel guide for a one-week trip.) On the other hand, surely Apple could let the developer choose if they wish for their applications to participate in such a trial program or not.