I know this is an old thread, but I've recently had the same question, so it's still relevant today, and the accepted answer is incorrect.
This RST driver is beneficial (though, strictly speaking, not "needed") even if you don't have RAID:
"Intel Rapid Storage Technology provides benefits to users of single drives as well. Through AHCI, storage performance is improved with Native Command Queuing (NCQ). AHCI also delivers longer battery life with Link Power Management (LPM), which can reduce the power consumption of the chipset and Serial ATA (SATA) hard drive."
For example, on my Windows 10 system after I've uninstalled the driver (also thinking it was useless and after reading some responses like the one above that it's not needed), my boot time has increased from 17 seconds to 27.