

For taxes: initially it was because business owners were renouncing their citizenship as a way to avoid income and capital gains taxes, as well as estate taxes. Once that was done though then the feds realized they could squeeze everyone.
For the draft: during the Vietnam War people would flee to other countries (usually Canada) and renounce their US citizenship, even if they didn’t obtain citizenship elsewhere. Becoming a stateless person was (correctly) seen as less of a death sentence than being sent to Vietnam.
Kinda the same here in Nevada. Our Spanish teacher explained them briefly but told us we didn’t need to learn them, didn’t test us on them, so on.