I wouldn't say that I need GPU to render my terminal, but if the alternative is to just let the GPU sit there, unused unloved, then I'll take the terminal that accelerates using the GPU.
Alacritty uses the gpu for acceleration, where iTerm uses it only sometimes. That might have changed in a recent release, but originally iTerm was limited in when it used the gpu.
I notices it a little bit when moving around quickly in NeoVim.