Why are we not allowed to enter a meeting room, unless the organizer arrives?

It is up to the organiser of the webinar to open the room. if they do it early you can enter.

Co-organizers can be specified in the setup (either when initially creating the meeting, or editing it after it is created); this allows others to be able to start the meeting. We try to add co-organizers anytime that more than one of our team will be in the meeting, this way we're all able to start the meeting. However, our clients or other collaborators outside of our team aren't allowed to start meetings.

The meeting organizer has the ability to allow attendees to arrive before them, but by default I believe that option is not checked. That option is set by the organizer at the time the meeting is originally scheduled, but it can be updated at any time.

The organiser is the person who activates the conference into active state . So its very much right that we have to wait for any person from the organising team to enable it.

The meeting organizer has the control over it. He/She can allow or not allow attendees to join the meeting before they start the meeting. This is not only with Go to meeting, it is there with most of the meeting applications.

Its a setting and depends upon the organizer whether he wants people to join before the meeting starts. Check with the organizer or the app admin.

Not sure