One of the things that makes music interesting and lively is variety in articulation and phrasing. Many composers coming from the sample world hardly ever think about whether a line might work better having it not completely as staccato or not completely as legato. Still, the difference of sound in possible variations is quite big. Just imagine a musical phrase of 4 eighth notes and sing or imagine possible variations of this. All 4 staccato, all 4 legato, first two legato second two stacc, first two stacc. second two legato. first note staccato, second to fourth legato with an accent on the second. All of these will feel and sound very different and especially the ones with mixed articulations will have a more musical feeling than the static articulations. Even though it might seem a little strange but it is really worth the time and effort to sing through a phrase that you’re just writing with possible different articulations to find the best or most interesting one. Of course, programming mixed articulation lines with samples is a nightmare and takes a lot of time but it is really worth the extra mile.