Laziness / efficiency. Some of the tools require specific kernel configurations/etc. to work properly (like wifi or bluetooth sniffers/fuzzers). These can some

Laziness / efficiency. Some of the tools require specific kernel configurations/etc. to work properly (like wifi or bluetooth sniffers/fuzzers). These can sometimes be either a) tricky to install, b)hard to get to cooperate, or c) mutually exclusive. Backtrack et. al. save the security practitioner a bunch of time getting a ton of tools in place all at once that are (mostly) pre-vetted to not do anything stupid, and to work together. Beyond that, if you're doing it professionally, most folks I know use something like Backtrack to get a new device setup, and then heavily customize/modify it from there. If you're doing it...for fun, a bootable CD leaves no logs and can be used on any computer on any network without having to pre-install stuff.