A parent can take the deduction only if they are personally liable for the loan. This means that Stafford, Perkins, PLUS Graduate Loans, and all other educational loans students take out for themselves will not be deductible for a parent because the student is the borrower

-follow this link for more  information on 1098-E-

IRS: About Form 1098-E, Student Loan Interest Statement

Makes sense. Yet my son can't take the deduction b/c I claim him as a dependent. So the interest goes "nondeductible." Disappointing.

Yes, it is unfortunate.  You could take the interest deduction if you had co-signed on the loan - then you would have a 'legal obligation' to pay the debt.  

You can claim the deduction if all of the following apply:

• You paid interest on a qualified student loan in the tax year 2020.
• You can take the deduction as a student, or as a parent making payments on your dependent student’s loan. However, you or your spouse, if filing jointly, can't be claimed as dependents on someone else's return.
• You're legally obligated to pay interest on a qualified student loan.
• Your filing status isn't married filing separately.
• Your MAGI is less than a specified amount, which is set annually.