You are probably quite right it is the promise of eternal life that keeps the faithful in line. Sad that it is based upon a lie !
But like all lies if is repeated often enough it is universally accepted.
It is based upon the old tales from the early pulpit, God sees all and hears all so you have to behave or else you'll end up in that other place! Kept the masses in check for centuries.
When the church wanted something done or built don't expect any fat contract or payment.... No you will all get your reward in Heaven !
The suckers fell for it and still do.... and why because no one has ever come back and said it’s all a big fat con !
But instead of accepting the facts that there is no great beyond to come back from the faithful duly go on accepting the old rhetoric. Not even the smell of coffee and wake them from centuries of brainwashing.
PS There's no Hell either.... that's based on the same bullshit !
If there is the great big reward for being good (Do what I tell you ) obviously there has to be a Bobby prize if you're bad !