So, why do prefer to consistently use the same exchange?
Easiness, convenience and also because it becomes an habit. You trust that exchange based on past experiences, so you keep coming back for more transactions. Our daily routine is already too busy to keep looking for new alternatives of exchanges to be used every new transaction we have to make. So we stick to only one, saving us time in the end of the day.
However, from times to times it's a good idea to check if the market has a better option available, especially regards exchange rates. Sometimes exchanges start charging expensive fees from customers suddenly. For that reason, it's important to have a Plan B.
Anyway, the ideal would be to adopt P2P transactions, where you could negotiate based on fair market prices (for both sides), but for most of us it's not a possibility, because there isn't who to trade with directly.
I will capitalize on past experience, like if you have a good experience with a particular exchange, you just feel comfortable and subconsciously you keep coming back to them. Also if the exchange has good a rate, that adds to one your user experience, and the interface is just easy to use and nice.
If it has good security to protect your funds, like overall you enjoy it, you find yourself coming back to it. And probably because you are busy and trying to keep up with the way life moves fast, you sometimes forget to even try other exchanges out.
Although it's good when you hear about a new exchange or something, you just give it a try, you might not do a serious transaction with it, but you just try with the least amount that you can risk, in case something goes wrong
So what makes me use one exchange repeatedly is how easy it is for me to use, the rates, no network glitches, the security is good, and their customer support system too is good, like all of this, just gives me a good experience and make me ignore other exchanges in the market, and keep using one.