Jump-statements Memes

"Rarely used" is doing some heavy lifting here. The textbook is basically saying "Look, we gotta teach you about goto because technically it exists and we'd be lying if we pretended it didn't, but please... don't actually use it." It's like your parents teaching you about cigarettes—they're not recommending them, they're just making sure you know what they are so you can avoid them. The academic equivalent of "we don't talk about Bruno." Props to the textbook authors for that passive-aggressive energy though. "Cannot say the jump statements have been covered" is code for "our editor made us include this cursed knowledge, so here it is, you're welcome/we're sorry."