the output impedance of a guitar is anywhere from 20k to 100k for most passive pickups. an onboard preamp brings this down to 500 ohms or so (or even lower). since the "standard" output level of a guitar is around a volt or more, and many effects boxes and amps are designed with this in mind, there's no need for an inline attenuator. the guitar's own volume control is often all one needs to get the output level they desire. there are also volume pedals, both active and passive. i used to make a preamp stomp box for people who didn't get ENOUGH drive out of their passive pickups to get the sound they wanted out of other stomp boxes and pedals (like fuzz boxes, etc...)....
BTW, just did a google search for one of the phrases in the OP..... the OP IS SPAM, as the identical post also showed up on 3 or 4 other forums like this one... as well as being posted by KevinXX (with the "XX" being various other things like "25" or "M2"
the other "attenuator" is known as a "Power Soak", at least that was what the original device was called back in the 70's. it was often used for studio work, but also was well suited for use with a "talk box" which was a compression tweeter with a hose attached to the driver throat. two people who used talk boxes were Joe Walsh and Peter Frampton. Aerosmith even used one in "Sweet Emotion"