All guitar players use effect pedals (a very generic, catch all term) .
Many times, effect pedals are the subtle tweak that creates the signature sound, often by adding some vague attribute to the sound, like "punch", "decay", "resonance",, etc . The Tube Screamer is a good example, it's just an overdrive pedal, but SRV turned it into one of the most desired sounds in the world. Eddie has the right combo of guitar, amps, effects & mixing to create an extremely unique sound.
Eddie used distortion, flanger, phaser and chorus throughout his career, but many of his signature sounds (ex. trem bar dives, tapping, pinch & pitch harmonics, ultrafast strumming) are pure skill, just better projected through effects.
/GuitarGeekout