Because you need a challange. Against weaker teams in LKL you always know that unless something truly extraordinary happens they will win. Kurtinaitis likes to make it more challanging like the point difference or for example in one game against Marijampole Suduva Rytas were allowed to let Marijampole score 45 in a game and with 4:36 minutes to go in the last quarter Marijampole had a three and the result was 44, and boy you should have seen how every Rytas player were dying on court to not allow that single point. And the succeeded Marijampole couldnt score a single point during those 4 minutes straight and Kurtinaitis had to take whole team to a restaurant (him paying all bills of course).
Kurtinaitis loved doing such challanges like that. The result was that Rytas never lost against a weaker opponent and usually won by an impressive margin.
But he is very strict. Kemzura looks like a kitten compared to him.
On the other hand, Kurtinaitis differently from Kemzura is not afraid to play young players heavyy minutes. It was Kurtinaitis who made Gecevicius a leader of the team though he was still very young, he gave 17 year old Jonas in his debut game 25 minutes and he was constantly using young Buterlevicius and use him well (something that coaches after him were never able to do).
Kemzura in 2010 was forced to play with young core but when he has a choice he prefers going for more experienced players while Kurtinaitis is much more daring coach in that regard.