The vibrations captured by the pickups are created by not just the strings, but by the body of the guitar. Just like an acoustic guitar that amplifies string vibrations via the soundboard, the vibrations that turn into the electronic signal from a guitar pickup are created, in part, by the body of the guitar.

 

Therefore, if the body of the guitar impacts the vibration of the strings, and the body of the guitar is made of wood, it makes sense that the wood used to build an electric guitar would matter a great deal.

 

A mahogany-body guitar will resonate much differently than an alder-body guitar, and both much differently than a basswood-body guitar. You can feel the difference, and that means the strings are going to vibrate differently as well.