Mnemonics are vastly overrated and the tricks you see with people using them are mainly a result of constant practice which could be achieved by other means.
"Gruneberg (1998) argues that the keyword method, in general, is inferior to rote learning in the longer-term retention of vocabulary."
Interesting article! I agree that mnemonics don't help you much with long-term retention, that's why it makes sense to combine it with a spaced-repetition strategy such as rote learning. However, mnemonics help you translate information into a form that's easier to process for the brain. Even if you don't actively use mnemonic techniques when memorizing meaningless information, you will likely end up applying such techniques intuitively.