I like working on planes, I tend to get a lot done - when in the right setting - and in Economy is not this.
@Matt Graham already discusses the table and privacy issues, but I'd also add its about shoulder space. If I'm using a laptop, I need to type or use the mousepad, and this means moving my elbows around and if someone is next two you this becomes very difficult. So generally in economy, work doesn't happen. Now If i have an empty seat next to me, that's like hitting Jackpot - business space for economy pricing!
Business is obviously much more suited to getting work done, well outside the periods that they're serving meals, which lets face it in Business can be quite extended, not that it's necessarily a bad thing, but in the context of getting work done, can be disruptive.
Aside from having the headphones as
@Matt Graham also covers, I use a bluetooth adapter so there's no extra cords getting in the way. Inevitably you'll have the power cord for the laptop - even more so as more airlines will ban the use of powerbanks. But one less cord from the headphones is a good thing. And now I've moved to having all my devices USB-C powered, so
a single adapter covers all my needs.
But regarding headphones I always try to use headphones/earbuds that have multi-device connectivity. That way I can listen to music through my laptop while working, but then switch to the Bluetooth adapter and use the seatback entertainment system when the laptop is closed up for meals etc.
I'm not too concerned about privacy, Luckily the nature of what I do gives me that freedom, andif anyone is able to figure out the things I'm doing - I welcome their resume
www.australianfrequentflyer.com.au
server browser. Impossible unless you have signal app I heard it’s used high up in the Trump Admin! 
