Savage is done for the initial satisfaction of overcoming the challenge, aiming for faster killtimes, sharpening your skills for the next tier, and gearing up for Ultimate.

It's just a video game. Yoshida isn't going to pop out of your CD tray, shake your hand and give you a life-altering quantality of money for clearing an Ultimate. You do it purely for your own satisfaction and to test your skills, and if it doesn't seem appealing than it may just not be for you.