Everybody fancies themselves as fantastic traders with the emotional strength to take on the most devilish price action the markets can offer. The problem is, stats don't lie -- retail traders have a low success rate after 1 year with most losing their account entirely never to return.
Some people advocate "Dollar cost averaging" -- the strategy of buying dips cumulatively as the price goes down and adding a fixed (or more amount at pre-defined levels). This kind of strategy suits the investor class much more than the trader. It is also the kind of strategy most employed by "hodlers." People like to joke that DCA is an ineffective strategy for optimal return and they would be right.
Money is best used when it is making a return and if you're deploying money as a market is going down, it will take time before it starts working for you, during which, there will be an inherent opportunity cost. Some bear markets can extend for years and years, followed by further years of sideways accumulation. For wealthy investors with long time horizons of 10 years or more, this probably isn't a problem, but for people looking to make more optimal use of their money, dollar cost averaging has very apparent weaknesses.
When is a good time to use DCA as a strategy? When the market has established itself as a bull market.
Remember, choosing to deploy your cash for an asset means that the person selling you the asset for your cash needs the cash more than you do right now. In the long run, it is expected (but not always the case) that delaying your expenditure in the short term, should reward you in the long term. Having a hodlers mindset is not necessarily bad, the difference is how to execute your strategy, and most importantly when to deploy your dry gun powder.
Most people wait till they've seen the price go astronomically high before they decide to buy in, and by that time, the market has already reversed. At that point, using any DCA strategy will not yield positive results. Sure, eventually with hodling, you may see a positive return, but it will be greatly out-sized by those who are patient and choose to enter once the market conditions are ripe.