Whilst I am a big importer, myself, I do understand why regions exist; admittedly, I wish Nintendo would give developers/publishers the option to release games without region checks. There are two main reasons for continued inclusion of region locks:
1. A developer can "sell" a game to several publishers, especially so if a particular publisher only works in one geographical region. It helps with deal-making if a developer can show to a publisher, in one region, that they're not going to end up selling against copies freely imported from another region. The problem comes when a developer doesn't make the effort to find a publisher in a region, or is simply unable to find one if they do make the effort.
2. Content in games, i.e. third party music tracks, special appearances of celebrities, etc, might possibly be only available for licensing in one particular geographical region, or it might be that their appeal is extremely limited in another region. This is very common in the case of music tracks, where different regions will have different track listings.