Trade vs Convert. Which one is better?

For normal users, like you and me, the payment is 0.1% per commerce, or 0.075% when you choose to pay your fees with BNB.

Nevertheless, Binance's convert claims 0 charges, so I was wondering what's the 'caveat'. If it's zero, what's the point of buying and selling via pairs?

IIRC, Robinhood used to say 0 fees too, however they profited by the bid/ask difference. So f.e. for those who needed to sell that X stock, and X was selling for 10$ every, Robinhood would misinform you and inform you it's bought for 9$ each, and pocket the 1$ distinction. When you needed to buy X, they'd inform you it's bought for 11$ each, and again, revenue 1$ for each stock you purchased. So that was technically zero fees, but very shady from their aspect.

I was wondering if Binance does the same in relation to changing? Trigger having 0 fees is unnecessary. On the end of the day, they still have to earn cash someway.