Same reason people want to lose weight but don't want to make the sacrifice of eating less and working out. If you can come up with a pill that convinces them they can, they'll buy it. So when they came up with a false Christianity that said you can sin all you want and be as selfish as you want and still go to heaven cause Jesus already paid your ticket, well it's been selling like hotcakes. Too bad it's a scam.
Freddy, your question is deeply philosophical. Great minds have dwelled on it for centuries. But, let me cut to the chase - some people are just dumb. That's it. With apologies to all those great philosophers and the effort they put in. People can be incredibly dumb. That is all.
These people claim to be christians, but want the rich to be richer and the poor to be poorer; they want wars on every horizon, they want sick people to die untreated.
And its not even like they ignore the gospels and focus on the old testament either. They eat abominations before the lord by the fistful at red lobster, and cant ram pork down their throats fast enough at Denny's.