For me, I'm trying to reduce the number of total files in shared network locations. Utilizing the mobile geodatabase is very attractive because it is a single SQLite file as opposed to the smorgasbord that is the file geodatabase. If the mobile geodatabase is the future of local database storage, then this should be an option you're able to toggle within ArcGIS Pro.
The implementation of the mobile geodatabase is not complete, just as the file geodatabase is never complete (eg an elementary thing like involution is not supported even after 16 years of fgdB development). In the current state Mobile gdB does not support eg raster field type, rasters dataset and mosaic (very important for every GIS repository/data storage). Externally, with the help of an SQLite manager, you can load raster data as Blob datatype, but it will be invisible and unreadable in AGP. Also, you cannot edit data loaded into the mobile gdB through AGP outside of AGP. ESRI has, therefore, reserved both types of databases for itself, but does not do much to implement them for users as a personal and local replacement for large RDBMS (but ... by the way, other players in the GIS arena are working even less on this). All in all, this idea can only be acceptable when ESRI implements all of the above, which I doubt will ever happen.
This Idea has been implemented in ArcGIS Pro 3.1. You can now set a mobile geodatabase to be the default for all projects, using the 'Options'>'General' tab in the backstage. Please see the What's New documentation for more new features in Pro 3.1.
The Ideas in ArcGIS Pro 3.1 blog will be wrapped up soon, highlighting all Ideas implemented in this release, including this one. Once complete, I will add the link to this comment.
Thanks @AmeliaBradshaw! Does this work for creating a new geodatabase for each project, or only if using the same geodatabase for each project? I don't see an option to specify a mobile geodatabase for the "new geodatabase for each project" option in 3.1.
Agreed, @AmeliaBradshaw I would expect an option here to specify the type of geodatabase to be constructed with each new project-- --the "new default geodatabase" is always a file geodatabase.
@jmaxwell_braun and @feralcatcolonist_old This idea was to use a mobile geodatabase as the default and in 3.1 that is fully implemented. That is, a mobile geodatabase can be set as the default geodatabase and that can be set to be the default for all new projects.
Wanting the option to create a new mobile geodatabase rather than a file gdb whenever a new project is created, though seemingly similar, is a different request. Please submit a new idea for that. It looks like the team is already going to add an issue to the backlog based on this discussion, but it will be best to create a new idea that we can link to that.