Why do the Underground lines have names?

Let's flip a classic question on its head. We've asked if the Overground and DLR lines should be named like the Underground, but why do the Underground lines even have names? Ko-Fi: https://ko-fi.com/jagohazzard Patreon: https://patreon.com/jagohazzard Just Watching Trains (2nd channel): https://youtube.com/@JustWatchingTrains-ji4ps Threads: https://www.threads.net/@jagohazzard Instagram: https://instagram.com/jagohazzard?igshid=OGQ5ZDc2ODk2ZA==