Nonsense. It's for the same reason that explains why Binance charges like $30 to withdraw in bitcoin. That gives you an incentive to trade into a shitcoin. Binance gets the BTC/LTC trading fees and liquidity for LTC sellers.

You pay three times -- trades BTC for shitcoin (e.g., LTC) on Binance, then pay a (small) fee to withdraw the LTC (e.g., to Kraken), then let's say you then convert LTC to USD there (third fee you pay), and then withdraw the USD.