Liquidity and slippage
When an investor submits an order on a crypto exchange, there is no guarantee that it will be fulfilled: as the size of the order increases, the chances of success decreases and the probability of price slippage goes higher and higher. In truth, neither market nor limit orders are a great bet for investors that are taking large positions.
Let's say an investor has a large sum of fiat currency that they would like to use to purchase Bitcoin. If they were to decide to submit a market order - agreeing to pay the current market price - they may find that they end up with far less cryptocurrency than they were expecting to receive. This is because the cryptocurrency exchange is not likely to have on their order books any sellers with that large an amount of Bitcoin up for sale. The exchange would need to split the order into smaller 'sub-orders,' and fulfill them one after the other. It is quite possible that the rate paid for later sub-orders would be higher than that of the earlier ones.
Limit orders, on the other hand, may be even more problematic. In this kind of order, the user of the exchange specifies at which rate they wish to purchase the cryptocurrency in question. The issue, here, is that the asset may never return to that rate, or it may take a very long time to do so. Then, it is not likely that a single seller will be listed on the order books that can fulfill the entire order. Large limit orders have a very low chance of success.Discretion
One thing that is very much misunderstood in the press today about cryptocurrencies is that their transactions are entirely trackable using tools called blockchain explorers. The wallet addresses of large crypto holders, who are frequently referred to as 'whales,' are well-known in the community and can easily be tracked using software, or by manually looking them up on sites like https://blockchain.com
This is not an appropriate scenario for certain kinds of investors, including high-net-worth individuals and companies. Even when full transparency is not an issue, significant and sudden movement by large crypto addresses can have unexpected consequences in terms of market price.