Agreed, mine can't read DRMed LRX either. Those were only sold by Sony, and Sony switched its DRM support to EPUB. I still have books that haven't been re-released, but only two.
The cautionary tale here reinforces "DRM is Bad." Because we bought books with DRM, Sony can decide to force us to another format. Regardless of how it looks on the reader, after the fact, without recourse. I have lots of LRX books, that still look better than EPUB on the 505, all because I made them from non-DRMed sources.
Don't blame the 505 because "DRM is Bad", just buy and read something available without DRM.