Why is the :port not merged into the params hash for the definition?

memcached_instance.rb

define :memcached_instance do
  include_recipe "runit"
  include_recipe "memcached"

  opts = params

  runit_service "memcached-#{params[:name]}" do
    run_template_name "memcached"
    default_logger true
    cookbook "memcached"
    options({
      :memory => node['memcached']['memory'],
      :port => node['memcached']['port'],
      :listen => node['memcached']['listen'],
      :maxconn => node['memcached']['maxconn'],
      :user => node['memcached']['user']}.merge(opts)
    )
  end
end

nore.rb

'node' => {
			'memcached' => {
				:user => 'nobody',
				:listen => '127.0.0.1',
				'instances' => {
					:obj => {
						:port => '11211'
					},
					:chat => {
						:port => '11212'
					},
					:grp => {
						:port => '11213'
					}
				}
			}
		}

recipe.rb

node['memcached']['instances'].each_pair do |name, options|
  memcached_instance name do
    params.merge(options)
  end
end