The modal switch is not just between the Library and Develop modules. If you're making a book in Aperture, you can make adjustments to the image by changing tabs, not going back to a module.
Never claimed that other modules weren't modules. I said the difference between modules and tabs is overstated. If I'm in LR's book module and press D I can tweak an image, alternatively I can click on the Dev name at top which I also thought of as being like tabs without the skeuomorphic tab design. The main advantage is the lack of clutter and reduction in clicking compared to Aperture.
And Lightroom's acceptance advantage probably has more to do with the fact that it's cross-platform than any perceived ease of use.
Actually no. A survey of pro photographers some years back who used Apple computers showed a huge uptake in LR and not much interest in LR and that was before Apple lost interest in the programme.