Because we do that with mosquito nets.
EA seems like a way to achieve nothing while looking like you're doing everything. No one expects you to fly to Mars tomorrow. And that's true every single day. It's true today. It'll be true tomorrow. It was true yesterday. It was true 10 years ago. It will be true 10 years from now.
So if no one really expects you to fully achieve your goal, all you have to do is kinda look like you're trying and that will be good enough for most people.
EA takes a good, hard look at all these good intentions and says, "Fuck, this would make a baller ass road".
However, if we solve malaria. That's another thing not killing us. Another problem checked off. Like polio. Or smallpox. Colonize Mars? Fucking how? We can't even get the environment on Earth under control. How the living fuck are we going to create an environment on another fucking planet. Much less even get there.
So how about we figure out a way to get the garbage out the ocean. On how to scrub the air of CO2. How to manufacture and produce without so many polluting side effects. We keep doing all these smaller things. Put in the work, and one day, we will save all those trillions of potential lives. But it requires putting in the work.
Edit: Not saying you believe it. But presenting the counter-argument to EA.