They probably have a philosophy that holding Monero is inappropriate, considering the possible sharp drop in price upon delisting.

The service fee increase is a loss prevention mechanism of our exchange and usually only affects highly volatile coins, which in that case was XMR. Don't forget that we don't resell Binance like other swappers, so charging 0.5% which often causes a loss of our own reserves is not always an option.

The first service fee spike for XMR pairs was caused by OKX delisting XMR.
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However, we are considering to keep 5% on selling XMR in future because our service is now used by many other services with a purpose of mixing, therefore it's absolutely inconvenient for us to work hard acquiring XMR then give it away for nothing to some other service that makes considerable gains based off our hard work acquiring XMR. Same for users who only use eXch for mixing their BTC through XMR - we don't consider it honest when some of them complain about 5% for the level anonymity they will take from our service without recurring to chaining their funds flow through different services that might cost them far more than just 5% (and who are often eXch's resellers).