well, they ARE, did you want to concat all .PDE and .JAVA files into one file?
i see no use of that unless for the purpose
- to post it here at the forum as one CODE?
- backup more easy? ( Processing / Tools / Archive Sketch works well )
but with smarter editor ( color marking, folding …)
no need to use multiple TAB / .PDE files.
but with one file you might loose the modular structure / re-usability
( of your classes and functions )
but as long you think in / use the project structure ( directory / pde files… )
both ways should be ok.