Key Switches vs. Many Tracks
The majority of sample libraries nowadays rely on so-called key switches. By triggering a (usually very low) note outside of the range of the instrument, you can switch to another articulation of the same instrument (e.g. switch between legato and staccato samples). This eliminates the need to have quite a lot of tracks in your DAW for the same instrument, where you would need to have one track for all legato notes and one track for all staccato notes etc.
While key switches are pretty comfortable to work with (especially once you have these key switches memorized) and can really save a lot of time when you need to deliver something quickly, they have one major downside: it is usually very tricky to layer articulations. While from a real orchestra perspective the thought of layering two articulation in the same instrument or section is something that is not extremely common, in order to create convincing mock-ups it sometimes is essential to do this.
The most common case would be the need for more attack on what your legato or sustain samples provide and achieving that by layering a staccato sample on top. This becomes even more demanding in lines that use even more variety regarding articulations where just switching between the available articulation creates too much of a difference in playing attitude and you need to mix various articulations at various intensities to get the line to sound halfway decent. The fact that these different articulations always have been recorded separately (which causes different playing attitude, embouchure etc.) makes it usually very tricky to simply switch between them in order to create a homogenous line without creating the feeling of constantly jumping between different worlds regarding the playing attitude.
So while it seems very uncomfortable and confusing to have a lot of tracks with different articulations for the same instrument instead of just a few with key switches, there definitely is an advantage to it that should not be underestimated. Of course, everybody has to find his/her own optimal working procedure but just relying on key switch patches might make it tricky to create convincing end results.