Demons tend not to respond to contracts as so many people of the past have used them to attain something they want and then break their contract. When a person feels desperate, he or she will draw up a contract. Over time, the person my chose to go to a priest and or invoke Yeshua to break the contract. After, the person has attained that which was promised of course. Often times the person already has in their mind that he or she will break the contract when making it, believing he/she is smarter than the demon. Given all the times demons have been used by people then treated badly, they know what would happen and generally find people undeserving of contracts.
Demons can see the outcome of their actions, knowing what a person will do before actually doing it, even if the person doesn?t. If a demon doesn't think it will work out well, he/she will not agree to the contract, it?s as simple as that.