Well, of course, singing scales is necessary as part of vocal training. It drills the student on Pitch, accuracy, breathing, phrasing, flexibility, and speed.
In Aria singing, the composer often leaves several measures (usually at the end of a song) for the Diva to do her vocal gymnastics and improvise, creating her own melodies based on scales and arpeggios. It is the high point of the performance, and brings down the house.
However, to throw those scales into the middle of a syllable(melisma) or slip them in between lines (a “run”) where they are NOT intended by the composer, is self-indulgent and does violence to the tempo, the meaning, and the continuity of the song. This is EXACTLY what “Divas” like Beyonce, Aguilara, and yes, even Whitney(RIP) do with the Anthem, and it is uncalled for and, IMNSHO, ugly and just plain stupid-sounding. Whitney had particular talent at vocal improvisation, but even she used to put runs in inappropriate places. It is unfortunate that, just because a singer has the ABILITY to sing these runs, they feel they have either the right or the need to pepper the entire song with them.
Aguilera made it worse by peppering the entire song with runs, and all of them off-key, too long, and disruptive.
I honestly don’t mind a little improv on the word “FREE” at the very end, but the rest of the song should be sung straight up with traditional phrasing and tempo. That way, when one gets to the climax, one can “give it all you got”.
Save the best for last, leave ‘em wanting more, and do honor to the Song.
I agree with you; but if they do it Whitney was the best.