In most cases coercion probably won't be as obvious as someone literally pointing a gun to your head (though there certainly could be a literal or metaphorical gun to the head in some cases). Typically it'll probably be something more subtle like: "Hi, I'm going door to door to turn out the vote. Have you voted yet? No? Here, let me help you fill out your ballot. I'll even turn it in for you."
Coercion doesn't need to be overt to be effective, just a small amount of social pressure applied over a large number of people is enough to make a significant difference. That's why typically there are laws banning campaigning right outside polling places. Now what if the "polling place" is the entire country, over a period of multiple weeks? How are you going to enforce that? And how can the electorate trust that it is being effectively enforced?
Coercion doesn't need to be overt to be effective, just a small amount of social pressure applied over a large number of people is enough to make a significant difference. That's why typically there are laws banning campaigning right outside polling places. Now what if the "polling place" is the entire country, over a period of multiple weeks? How are you going to enforce that? And how can the electorate trust that it is being effectively enforced?