I can manually remove them as well, and do it for others all the time, but I prefer to take the slightly safer road and have one installed and running anyway on my Windows installs. I prefer Nod32, it doesn't have a large footprint on resources, and I can say for certain that nothing has gotten in in several years. It also really depends on what OS and what you do on a particular machine whether it is warranted or not.
On linux, it is a waste to even install one and I don't.