There are two primary reasons people use filler words.
One is to maintain possession of the role of 'speaker' in the conversation because, if you stop for a while, someone might think you're done (if it sounded like the end of a thought) or have broken down trying to think of what to say. Spending time in environments where people have high demands for time or competition for attention can make these things worse. The other is social fear or anxiety about how your message will be received, or over one's correctness and certainty. 'I am claiming this thing for myself,' has the same ultimate goal as 'Nah, lowkey f'real, I was kinda maybe thinking of nabbing that,' but the use of the extra 'filler' words and slang is designed to obfuscate the meaning, making it passive agressive, forcing the listener to parse the extra layers of obfuscation before having a chance to object, and leaving a verbal avenue of retreat open if someone does object, allowing them to say, 'No, I said I was thinking about it.' Spending time in environments where one has to deal with openly agressive people can often make people seek out these verbal conflict avoidance techniques.