there is nothing that requires a perpetuals market to have a lower volume than the whole spot market for the underlying asset. perpetuals are derivative assets, the reason they exist is to enable trading regardless of access to the underlying asset's supply.
side note: Binance will shut down their XMRUSD perpetuals with the delisting, but they will keep running their XMRUSDT perpetuals (USDⓈ-M XMRUSDT):
Please note that users may continue trading USDⓈ-M XMRUSDT and ANTUSDT Perpetual Contracts.