I'm going to assume we're talking about bitcointalk accounts here.
The value of accounts are still there, even if the trade for accounts seems to be in a 'frozen' state. As long as signature campaigns are alive, the accounts will have it's value.
Even without signature campaigns, sold accounts help people trying to scam via taking out no-collateral loans based on trust or just scammers in general.
Most of the time it seems like selling your account is just taking a cut of a loan scam, just without being forced to admit the fact that you're involved in a scam.