Well a product being used for illegal, unethical or immoral activities can very much be their business. If a user of your software used said software to to assist him in a criminal or damaging act then you the creator of the software are on the long line of parties being sued or potentially even prosecuted. By stating the intended use and the explicit uses that are not allowed, you absolve yourself of responsibility for damages due to users breaching the terms of the Agreement that they had accepted.
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The other reason why a EULA may forbid certain uses of software by end users is to avoid potential associations or affiliations that could be damaging to the organizations reputation. In the example above, the fictional company ChristiansMeetup.biz could suffer reputation losses and have their bottom line hurt by allowing the intended use of its software to this particular end user.
Finally, your analogy with the car is flawed.
One can and certainly does lose the rights to drive for repeat dangerous traffic violations.
One must accept the rules of driving and pass tests on these rules to prove competent enough to drive. Driving is a privilege not a right.
A legal contract between you and the car manufacturer over intended use is completely unnecessary as there are explicit laws that already define what the drivers behavior should be. The car manufacturer doesn't have to worry about defining intended use because the government does that for them, and also states that the manufacturer is not at fault for driver errors.
A EULA is a legal contract and it exists specifically because the laws and regulations may not be existant or may be fuzzy on certain aspects.