My little brother is a fire fighter. He tells me it's involuntary. At a certain point the heat and smoke get so intense that you can't do anything but jump. He's seen his trained collegues do it.
Nothing like that would have helped in the wtc.
https://www.technologyreview.com/s/425276/the-best-way-to-ev...
https://www.chamberofcommerce.com/herndon-va/33439780-skyscr...
https://en.m.wikipedia.org/wiki/Emergency_evacuation
https://en.m.wikipedia.org/wiki/Fire_escape
https://sourceable.net/tablet/single/?name=high-rise-fires-r...
http://emergency.cornell.edu/building-evacuation/
In short: there are systems, and they work, to varying extents, for existing structures. Very tall supertowers are a particular challenge, as every internal safety system competes for space with other interior uses, and external evacuation systems are difficult to specify and design. Many possible systems would have been compromised, internally or externally, on the twin towers, from the same extraordinary threats as were compromising the structure itself: gross physical damge to the structure, which closed off internal stairwells, and a raging, jet-fuel-fed inferno, which was weakening steel structural beams, and which would have compromised numerous possible esternal escape structures based on natural or synthetic fiber rope or tube systems.
Aerial evacuation was similarly hampered both by smoke and by lack of rooftop access (doors to the WTC roofs were locked against internal use).
The most effective protection was simply not to be in the towers when they fell. The decision of some survivors to leave WTC1 after witnessing WTC2's strike was key, and the in-building announcements to not evacuate contributed directly to the death toll. The inhabitants of WTC2 above the impact zone were doomed in all but the most optimistic scenarios, which is troubling -- the situation bears some resemblance to the disaster on the RMS Titanic in 1914, for which I strongly recommend the 1954 film A Night to Remember.
It's worth remembering that the daytime occupancy of the WTC complex could exceed 50,000, and estimates are that 17,400 people were in the towers at the time of the attacks. Over 84% of the occupants managed to escape successfully (the death total of 2,753 includes both the hijackers themselves and occupants of the two flights which struck the towers). That's a grim success under the circumstances.