Using a harmonizer is much easier than dealing with the thousands of musicians that say they know harmony and just try singing the lead line badly. I honestly have met very few musicians that know how to sing a harmony..
That is a big reason I went solo. I never get attitude from the gear, nor do they show up to gigs drunk. and they know how to do what I want them to.
I have 3 mandolins, 2 mandolas, 2 octave mandolins, a mandocello, bass, banjo, 1 acoustic and 2 electric guitars (2 are midi capable), harmonicas, bongos, drum machine, 24 track, 5 mics, 2 PA's plus assorted support gear. So my tech is a lot more than just a harmonizer lol. I took 2 years of studio engineering as well and like that end of the music. Nowadays it is affordable. When I finished my course in 1992 you couldn't even buy cd burners and adat players just came out... it was about 12 grand for an akai beta 12 that used beta (not vhs) tapes to record.
now you can have a studio setup with everything for $5000 or less. To say we don't need tech? everyone uses it to a point unless it is a totally acoustic show with no PA. otherwise there are delays, reverbs, eq's and such all being used on just vocals, let alone what guys use on their instruments like wah and overdrive.
I should add in recordings, I actually sing the harmonies. but live I use the harmonizer