Many people worry on their privacy from wife or parent. With ATM card in your bank statement you will get transection detail associated with porn site. But with bitcoin you will receive no transactions statements. That is the advantage bitcoin has brought to us.
Or if they cheat their wives.
It is immoral to cheat your wife but its not illegal. So if a person wants to cheat his wife he has the privacy to do so.
I`m not endorsing wife cheating, but some people will do that anyway.