There's a number of issues this could bring up, and not a whole lot of benefit. Surely you can help your friend and other new players, but what's to stop other players from straight up trolling them during the match? Giving away locations, providing bad advice, etc. The novice matches allow for players to learn the basics of the game without the added stress of having a high level player give orders you don't understand, or constantly destroying your ship and stomping on your team.
Overall, the time players spend in novice matches is pretty brief before they're forced into non-novice matches, where you need to add onto the basics you picked up, and you learn a lot more practical aspects of the game. It's a bit of a sharp learning curve, but if you fly under an experienced captain, or find a lobby where players are around the same experience as you, it's a bit easier and less stressful.
Back to the main issue, the benefits of being able to spectate the novice matches probably isn't worth the time and energy spent building a system that allows for it. There's also the upcoming matchmaking system which should alleviate most of the "I can't play with my friend who's new" issues.
(And by the time that matchmaking is finished or they put in a system that allows you to join or spectate novice matches, your friends should already be rank 4 or higher in a role)