I see a lot of examples of nginx.conf using a reverse proxy similar to this:

location / {
  proxy_pass frontend;
}

location /api/ {
  proxy_pass backend;
}

But why not serve the frontend as static files similar to this?

location / {
  root /usr/share/nginx/html;
  try_files $uri /index.html;
}

location /api/ {
  proxy_pass backend;
}