Why do I need to import collections in router file? - mongodb

Question

I'm building simple webs with meteor, just to get to know each other, and I'm playing with iron:router as router.
The "problem" I got is that in my meteorapp/lib/routes.js I need to import my collection file which is in meteorapp/imports/ui/reservations.js:
import { Reservations } from '../imports/api/reservations.js';
Otherwise I'm not able to reach it in the template, even though I imported it same line (different path) in the templage.js file like this:
import { Meteor } from 'meteor/meteor';
import { Template } from 'meteor/templating';
//collection Reservations
import { Reservations } from '../api/reservations.js';
import './roomSchedule.html';
Template.roomSchedule.onCreated(function roomScheduleOnCreated() {
Meteor.subscribe('reservations');
});
Template.roomSchedule.helpers({
allHours() {
return Reservations.find();
},
});
I don't know if this would help, meteor list output:
user#laptop:~/Documents/meteorApps/mymeteorApp$ meteor list
blaze-html-templates 1.1.2 Compile HTML templates into reactive UI with Meteor Blaze
ecmascript 0.10.3* Compiler plugin that supports ES2015+ in all .js files
es5-shim 4.7.3 Shims and polyfills to improve ECMAScript 5 support
insecure 1.0.7 (For prototyping only) Allow all database writes from the client
iron:router 1.1.2 Routing specifically designed for Meteor
meteor-base 1.3.0 Packages that every Meteor app needs
mobile-experience 1.0.5 Packages for a great mobile user experience
mongo 1.4.3 Adaptor for using MongoDB and Minimongo over DDP
reactive-var 1.0.11 Reactive variable
shell-server 0.3.1 Server-side component of the `meteor shell` command.
standard-minifier-css 1.4.1 Standard css minifier used with Meteor apps by default.
standard-minifier-js 2.3.2 Standard javascript minifiers used with Meteor apps by default.
tracker 1.1.3 Dependency tracker to allow reactive callbacks
So it works... but don't know why... Thanks in advance to everyone.
Axel.