No, they're not. There are three reasons why your crypto assets are not safe in a coin market.
First, the purpose of a coin market or crypto exchange like Coinbase or Binance is not to serve as a place to store your cryptocurrencies. Instead it was meant to serve as a facilitator for trade where users can easily transfer assets from one account to another. This, in itself should indicate that while there are security measures in place to protect your coins, the main goal of a coin market is to make it easy to move your coins. And unfortunately, this just makes it easier for thieves and hackers to move your coins into their accounts, as well.
To make things worse, whereas a robber has two problems when robbing a bank or casino--to get into the vault and leave the establishment to freedom--hackers of crypto exchanges only need to accomplish the first thing, which is to get into your account. Once that's done, they're scot free. In this respect, your assets may not be safe on the coin market because the coin market was never meant to be a place to store your assets.
Second, another reason why your assets may not be safe in a crypto exchange is the fact that they are hot targets for thieves and hackers. And why not, crypto exchanges hold large amounts of cryptocurrencies at any given time, which makes them rewarding targets. Just consider the June hack of South Korean-based cryptocurreny exchange Bithumb where thieves made off with $31 million in cryptocurrencies, or the infamous Mt. Gox attack, which lead to the loss of 7% of the world's Bitcoins.
Granted, there are coin markets like Coinbase Pro, which claims to be unhackable. However, the problem is, even when a site-wide hack does not happen, individual accounts can still be targeted. And it's so easy to target individual accounts. Click on a wrong link and you could be the victim of a phishing attempt meant to crack your coin market password.
And finally, the biggest reason why your crypto assets are not safe in a coin market is the fact that you don't control the private keys to the wallets in your account. In exchange for the convenience of using a coin market or exchange, you are given personal wallets to store your currencies, which you access not by using a private key, but by confirming the username and password combination to your coin market or exchange account. This is because the private keys to your wallets are controlled by the coin market or exchange.
This is all well and good. Unfortunately, we have no guarantee that the coin market or exchange will stay as a trusted party forever. They could decide to steal your keys and the cryptocurrencies in your wallet, anytime. Or the company running the coin market or exchange could be dissolved, leaving you without access to your account.
It is for these reasons that it is not safe to store cryptocurrencies in a coin market or exchange. Instead, most active traders would only leave a small amount of cryptocurrencies, enough to cover a few trades, while leaving the bulk of their assets in a personal wallet elsewhere.
Sources:
- Crypto Exchanges Are NOT Your Banks. https://hackernoon.com/crypto-exchanges-are-not-your-banks-95c336f6b747
- Why bitcoin exchanges keep getting hacked -- and how to protect yourself. http://www.latimes.com/business/la-fi-bitcoin-exchange-hack-20180621-story.html