If you're a compleationist, you may choose to pay the additional cost of 2 life even if the spell's own costs wouldn't be reduced this way
Well, like saying OJ is guilty, nobody can prove it, but most people are pretty sure
You can also work your way around giving Yshtola Curiosity, so it hits for 2, you draw a card, cast the card youve drawn, and continue draining your opponents out with more triggers
With support like Liliana's Triumph and Syphon Mind, Kefka snowballs into absurd advantage and becomes nearly impossible to outpace
Some Kenrith builds also skew more towards group hug territory, which can also be fun to play against
While it doesnt add extra mana, it does ensure youll have access to all colors at all times