Or you can use some coin swap service for quick swaps... I have the amount on the exchange that I use for trading, it's not big, and I don't wish to pay withdrawal fees after every trade I make. I am an amateur trader, and I don't trade with some big amounts so I don't feel some big need constant moving of my trading capital. What you are saying is fine and advisable for people who trade with big capital.
Aw, I didn't think about the withdrawal fees. As every swap also contains some fee.. I usually store all the funds on my wallet and withdraw it according to my needs with a concrete person from my country. So fees are everywhere, I guess, but the services I use have the lowest one that I don't even mention.