where is the bitcoin mostly used after speculation on the markets?
Mostly online services. VPN/proxy services(Mullvad, PrivateInternetAccess, etc), server and domain hosting services(NameCheap, Vultr, etc), gaming black markets(Sythe, etc), computer hardware(NewEgg), sports betting(NitrogenSports, etc), and such.
what is the area of economics that dont work without bitcoin ?
I'm not really sure what you mean here lol.