Lumin was originally designed with the objective of playing music from a NAS running MinimServer. The Lumin app was designed to work with MinimServer. We have always believed in the model of player-library-mobile app (or client-server-mobile app) architecture - you can have multiple Lumin playing from the same library. This can perhaps considered to be a philosophical choice, and also answers why we do not provide a Windows app. We have always envisioned music playback to be done on the couch using an iPad (now you may also use iPhone or Android device), iPad was even a mandatory requirement for many years.
I know that this design does not suit everybody, but then no product is. I understand the appeal of a single all-in-one device with the library inside the player, I really do, but that is not our choice. I can think of various downsides with having the library inside the player for SQ impact, less freedom with library management and implications for repairs, although I acknowledge that our competitors and those who like their architecture would not agree with me. (Three months ago during an audio show there was even a lady who asked me for an all-in-one player with built-in DAC and Roon Core. I did not tell her this is just asking for trouble, but there are now evidences that I'm right.)
Nowadays there are more users who stream only from the Internet without having their own music libraries. For this type of users, our architecture makes much more sense than our competitors.
For Roon users, for those with the library inside competitor's players, the data flow becomes very odd - the music data is retrieved from the player to the Roon Core, then Roon Core sends the data back to the player for internal DAC playback or output to an external DAC.
When Lumin A1 was launched in 2012, it did not even support USB drive. USB drive support was only added 10 months later. Indexing of directly connected USB drives were avoided for performance and technical reasons.
While L2 is indeed an added expense, it is not mandatory. One may just use a fanless QNAP and run the free MinimServer instead at a much lower cost.