BNB buys a fee discount
Paying trading fees in BNB on Binance cuts them by roughly a quarter. For an arbitrage trader that is no detail: the difference between 0.1% and 0.075% per trade moves the threshold at which a route is worth taking at all.
A small BNB balance pays for itself under active trading, purely through the discount and without any bet on the price.
A house coin
BNB's liquidity sits mostly on Binance, which creates an asymmetry: books elsewhere are noticeably thinner. That is precisely why gaps appear more often than a coin this size would suggest.
The flip side is that a thin venue's book may not absorb your order. Look past the percentage at how much actually rests at the best price.
The BSC network
BNB lives on BNB Smart Chain, where a transfer costs tenths of a dollar and takes seconds. BNB is also the fuel there: the fee for any transfer on that network — including USDT BEP-20 — is paid in BNB.
Network care is critical. The coin also exists as BEP-2 on the old Beacon Chain, and sending to the wrong network is an ordinary way to lose money. The exchange shows the network on withdrawal; match it against the one the receiving side states for deposits.
