1) Waste's time - the person lying gets the wrong answers back because the wrong information was given i.e waste of time conversation, situation.
2) The truth always outs - it will take longer for the truth to come out with a lie but it always comes out eventually.
A so-called white lie i.e not full disclosure, may be acceptable if its to protect the recipient from something unnecessary for them to know, perhaps to reduce the word count, but that is not lying i.e to speak falsely or utter untruth knowingly, with intent to deceive. That has nothing to do with talking about something one doesn't know about, that's unknowing, misinformed etc. which has a link to lying but isn't the same. Withholding information is also something different as is concealment and open-concealment.
Billy Meier has not lied, so we are able to follow the explanations given in his books, we probably wouldn't have bothered if there was lying, and ask anyone who has read it all, there aren't any to the best of our knowledge, with what we can check.
Its a bad idea because it destroys community and friendship making
The best recommendation is to tell the truth even if you know its going to lead to something bad like a punishment. Its ok to release information strategically e.g to ensure you're being listened to, perhaps so that the apology is more meaningful. But tell the truth, its always the best way.
Telling the truth when something particularly bad has happened can even turn the entire thing into a positive sometimes; if its told quietly but clearly, calmly and sincerely with an honest apology - occasionally. But certainly a better outcome.
Film: Marshall (2017) - Courtroom drama about lying.