This sheds some light on the practice:
Coinbase is a great site to get started with and to purchase a base currency. To instantly purchase a currency a credit (debit) card is ideal. Coinbase actually offers some of the lowest credit (debit) card buy/sell fees in the industry.
It is recommended to use Gdax for withdrawing coins as they have no withdrawal fees. Transfer your coins to GDAX for free then withdraw from there to binance!
GDAX shines when it comes to saving on fees. Trading fees are typically .25% or less. You can see the specifics on their fee structure page. Coinbase charges ~1.5% when buying or selling via bank transfer and ~4% when using credit cards or PayPal.