Trading with market orders is generally like playing with fire. If you're comfortable with the current market price, just place a limit order at or slightly above market price, and it will usually fill.
Telling the market: "I want to trade now, and price is completely irrelevant" can be a recipe for a bad time.
How do you figure? People in cryptocurrency are already not afraid of the rampant volatility so this move seems to protect the broker and not market participant.
This also raises another question - whether these guys have stop orders? Because stop orders actually become market orders once triggered and help people get out at whatever price possible. Turn this into stop limit and it tries to find the "best" price possible and many people left holding the bag if things go south.
Placing a market order is equivalent to saying "I'll accept $0 for this asset, so long as that was the best price available." Only most people assume it means "I'll pay the number shown, or something close to it" which is only true of relatively stable assets on markets with plenty of liquidity. Making only limit orders available forces the market participant to choose what range of prices they would find acceptable.
Why doesn't an order type exist like: > "I'll pay the number shown, or something close to it"
? Like: acquire/lock all units to fulfill me market trade and if it is less/more than what i expect, cancel.
Most people don't realize a limit order isn't "buy at this price" but rather "buy at the best price in my favor, but don't spend more than this much."
Fill-or-kill means don't put it on the books, just get it now or cancel. You can also typically specify whether it is a partial fill-or-kill too (get it all or none at all).
Of course that doesn't stop low-latency firms exploiting information differentials to get their bids in before your order makes it to the exchange, a process called front-running. It would be illegal for your own brokerage to frontrun you, but pretty much all discount brokerages sell information to third parties, which enables those third parties to front-run. Ever wonder why your Robinhood trades are free?
A couple markets have had flash crashes down to pennies. Imagine placing a market sell order right before that happens, selling your bitcoin for $0.15 instead of $15,000.
In reality you're usually somewhat safe, but market orders are always a small gamble for this reason.
Things work in these limited conditions and then people claim victory, like they are doing with the bitcoin futures. We haven't seen the full market force out yet.