You know there are people who are citizens that have never been to the US. Why should they have to pay to renounce citizenship? If $Forefathers_nationality told you that you were a citizen and that you'd have to pay taxes, how would you feel about that?

Then there's Boris Johnson, British PM, and until recently US citizen. What benefits do you think he would have been getting as a US citizen abroad, over and above diplomatic protections he already had as MP and member of Govt?