Was thinking the same, every dip is a good buy. If it goes down at least you don't buy at ATH and if it goes up that's part of the reason why you bought the dip in the first place.
The truth is people can't know what direction the market will go and just buying dip seems like the way to go for long term. Treating buying dip as just reallocating portfolio make sense.
It's just that sometimes people aren't quite confident that the decline happening will be the right moment to buy. So, some people who are just starting to invest think about waiting for the price to really drop because they don't have a good plan or analysis.
Especially if the market situation drops and then they buy, but the market tends to move down even further. Such situations make beginners tend to choose to wait for the lowest price. In fact, we really can't predict it.