Some of them of course are invented whole cloth. British Received Pronunciation was invented and needs to be learned and is the standard of the upper class. It's neither right nor wrong but it's there to differentiate.
You say “needs to be learned” but that’s no more so than any other accent.
We just grow up with it because it’s how our parents and the parents of our friends speak.
If you want to change your accent you can, of course, get elocution lessons but most Brits do not. We just have a large variety of accents of which RP is one.
"Received Pronunciation was invented"
How so?
RP isn't really a thing any more, except among some of the older aristocracy and Tories and a few legacy BBC Radio shows.
Most people have settled into Estuary, which has split into a high/corporate/media Estuary-tinged dialect, and low street Estuary. The BBC has its own special neutral version.
Fifty years ago the difference between upper class/BBC/RP and street English was almost hilariously obvious. Watch a BBC show from the 50s and 60s - even something like Dr Who - and everyone is speaking a unique RP dialect that doesn't exist any more.