Free riding is a problem with public goods but not with private goods because for the private good:

Question

Quizplus · Accepted Answer

Free riding occurs when individuals benefit from a public good without paying for it, as they cannot be excluded from using it, and this results in underproduction of the good. However, private goods are excludable, meaning that access to the good can be restricted and payment can be required before allowing access. Therefore, free riding is not a problem with private goods as individuals who do not pay for the good will be excluded from using it.

Free Riding Is a Problem with Public Goods but Not