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.
In media, you’re quite correct - it has become rare bar presenters who are now in their 80s or older.
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.
I didn’t have lessons for it and I don’t know anyone else that did. It’s just how we speak.
How so?
Interestingly, the sociolinguistic literature shows that such a consensus is strongest among an aspirationally upward-mobile social group rather than the already social elite. In other words: The aspirational middle class make a big effort to speak how they think the upper class speak in hopes of joining them one day.
You don't have to follow them, but you do you should be ready to accept the consequences of your choice.
In the area I grew up in, caring too much about useless aesthetic stuff like “elbows on the table” would have a social cost.
