Niqqa..
I been rapping since I was 9 YO. Slang is everything. Not popular words per se, although people need to know what you're saying..
Everything I say I try to use the best word to describe the thing.
For example. The word 'fear'. You can say
scared
frightened
terrified
There's many words. But each word has its own shade of meaning. Terrified is different than nervous. Shocked is different than apprehensive.
The more words you know, the more information you're able to transmit efficiently.
So called slang has usages that proper language does not contain.
Like when nikkas say "I be chilling right here".
That doesn't mean "I am currently standing here"
It means "I do this regularly. If you come here tomorrow, I'll probably be here. Chillin"
When vultures and detractors make fun of or misuse the term, they use it wrong. AND there no proper equivalent. You can say "I am often found chillin right here" or "I be chilling right here"
Old slang. New slang. Foreign words. The important part is that it allows you better ways of communicating.
Knowing more and better words IS greater understanding and greater knowledge. You cannot even have certain thoughts without the right words.