A "life" sentence here means 25 years. It is life though, literally. They will never find a career when they get out, their record and rep. will forever be ruined, and 25 years is a long time. Imagine if you went when you were 20, and you got out at 45. That, along with a forever tainted record, is literally having everything in your life, taken away from you.
But I see what you're saying. Giving someone 125 years seems so silly.
Another thing is keeping them alive all that time too. Us, the taxpayers, are paying to have them stay alive by having a roof over their head, food daily, cable TV, at no expense to them. It's pointless keeping someone alive for that long, just for them to serve no purpose to society, and have them die in the end, giving nothing back.
Spend $100 on a 9mm, get a bullet, done.