What the OP said might be truth because with some good information about the past price of Bitcoin one can easily tell or predict how much it will be next time.
However, most of the times some predictions are might not be accurate but there will definitely be a day or time when one can predict the actual price of Bitcoin.
I also don't think that Bitcoin will ever decrease to $20 or $15k in future because it will cause a serious commotion that a lot of people will buy and hold it, both those that do not have the money to buy the Bitcoin at that time will want to borrow and buy (which is not a good idea).
The reason why I said it would be good to know the past price of Bitcoin is because it might help an investor to know when Bitcoin will increase or decrease.
Analysing past price can help but I think it won't give us an assurance. If only that how easy things work, many of us are now millionaire

. Like you, I also think BTC won't fall that low. It seems impossible right? Based on how things are looking right now in Bitcoin. What is more possible is that BTC price go through the roof. But if let say the other occurs, yes it will cause a commotion.
Though I think many people are going to sell than to buy because they think it's the start of the end of Bitcoin. Borrowing money to invest can be a good idea "IF" you know that the coin will still recover and rise for more. I know this can be the case for BTC now, but it may take a long time to happen, so it is still not advisable to do.