Hi KT,
the idea behind the DEV_ users was to use a different database user than the one the application itself is using (the NEO_ user), so that this DEV_ user can be tied to an personal user for the purpose of better traceability who was doing what in the HANA system, and also to allow a better access control (e.g. revoking certain privileges from such a "Development User" while retaining them for the application user and for other developer users in the same account).
Having said that, for the Trial accounts this may well be perceived as unnecessary overhead (and it might be just that), since in Trial accounts you usually have a one-to-one relationship between account and user.
But don't expect this to change in the Trial offering we have today. Bigger changes are on the way, as we plan to change the HCP HANA Trial offering more fundamentally in a way that makes the development experience much closer to what you get for productive instances.
Best regards,
Oliver