Perhaps you can understand some psychology, as applied to children. When you set a curfew, or other rule for your teen, and they break it, would continued "amnesty" for any consequences teach the teen to stop breaking the curfew? No, so why have a curfew if it's not enforced? Would you reward your toddler with cookies when he/she hits their sibling after you had told them "don't hit"? No, so why bother having a rule against hitting if you reward them for that very behavior?
Repeated amnesty emboldens and encourages even more illegals to come into this country because they already know that if they can't get it this time, there's another one down the road and in the meantime, they've been "taught" they can ignore the immigration U.S. rules/laws with impunity. And if those laws can be ignored.....maybe they can ignore all the other laws they choose.
When rewards are given out after rules/laws are broken, it encourages more of the very thing the rule/law was put in place to stop.
What's the logic is that kind of system?
That's a false analogy because you're rewarding the exact same person who will engage in future violations. Your analogy also contains no additional disincentive for the person to engage in that conduct. That's not the case with amnesty for illegal aliens.
The primary reason I would be willing to accept amnesty isn't because I think its a "good" idea on its own, but because its something I'd have to give up as part of a compromise to get proper border enforcement.
One small virtue to amnesty is that it would create a better database to control present and future immigration. Right now, illegals go to all length to avoid immigration authorities. That means they are completely unregistered and can move in society without being tracked. If you did an amnesty, then the current crop of illegals have an incentive to register officially, and give us some clue as to how many we have. And if you coupled an amnesty with significantly greater employer penalties for hiring illegals who haven't been granted amnesty, you make it much tougher for "new" illegals to get jobs.