Eventually the 20th Century History class at Starfleet Academy stops being a fringey elective and becomes a required course, and all the cadets are like “this is so irrelevant, why do we have to learn this” and anyone who’s been around for a while is like “there is an 812% chance that you will time travel to the 20th century during your Starfleet career”
"but the temporal prime directive"
"At the very least you will get trapped a holodeck program based on the 20th century, and you will need to know all these weird idioms"
"But why is it only the 20th - "
"We don’t know why it’s only the 20th century we have a whole corps of scientists trying to figure out what’s happening with that it seriously makes no sense but in the meantime, knowing how to work a combustion engine is pretty much guaranteed to save your life so get the hell on that."