Yesterday, whilst flying low over various cities, i watched the “task manager” internet data usage my end. Whilst i have now 500mbps of grunt, why does the sim only rise to a max of 170mbps whilst spawning photo realism?
As i fly, things pop in right in front of me, but surely if the sim made use of 97% of my internet speed, it would be flawless.
Question, why dont Asobo make full use of the individual users data stream?
I monitored the stream for a while and I can say:
Over 98% during your flight you will never max out your internet connection.
In my case I had a consumption between 10-40 Mbit (using a 200 Mbit fibre connection).
The reason why you will never reach a full usage its simple:
You share your internet connection - finally the Azure server @Microsoft with other gamers. You don’t use a single port oder space on their servers for your own gaming.
Sharing is everything. Flying is everything. Have fun. Together. 
About why MSFS isn’t using all of your internet speed…
It’s not just about the game itself. Think of your internet connection like a pipeline.
When you’re playing a game online, it’s not just the game that’s using your internet – your system needs some of that bandwidth too.
First off, your device needs some internet just to connect to the game server.
Then, once you’re in the game, there are other processes running in the background that also require internet access, like updates, syncing game data, or even just maintaining a stable connection.
So, while you might have, say, 500 Mbps internet speed, not all of that is going directly to the game.
Some is being used by your system for these other tasks. Plus, there are often limitations on how much bandwidth a game will use, both for technical reasons.
Think of it like traffic on a highway – even if you have a fast car, you’re still limited by the flow of traffic and the speed limit.
Similarly, your game’s internet speed is constrained by various factors beyond just your connection speed.
When you saw it peak, how long did it peak for. In other words, did you see something like this:
Or this:
It could be that for the amount of data you need to download it never gets the chance to reach its higher speeds as the download is over before it can stretch its legs, so to speak.
For example, if you were downloading lots, and lots of small files, you would see many of the second example, where each file is downloaded, and a new one started. Whereas if all those little files were in a ZIP file, you would see a longer version of the first example, as a single file is downloaded over a longer period of time.
My guess is the sim would prioritise scenery tiles in front of the plane, downloading them a tile at a time. You performance might also be affected by the speed of your plane, putting more load on the system the faster you travel. If you are slow, a slower network connection may not be as much of an issue. But it won’t download all the scenery for your entire flight, so will download what it needs to when it is needed. A related behaviour can be seen watching YouTube. It never downloads the entire video, but just enough to allow you to watch it without interruption. They do this in case you click away from the video, which would cost them if they just sent you the entire video on a fast connection.
I’m not sure MSFS could use all of my bandwidth … 
In addition to the other comments and explanations - It also could be limited by the speed on the other end of the pipe… or the speed somewhere along the (long) pipe… if MSFS/Asobo servers can only deliver at 170mb/s, then you aren’t going to get 500mb/s of data.
Your implied assumption is that the game is being limited by the rate at which data is supplied from the internet. Could it not possibly be that the game is drawing as much data it requires at the rate that it requires and that the rest of your system is the constraint? Basically that it cannot use more data faster than that? Is there even a way in the game - using the Dev mode frame time display for instance - to see if the system is being “starved”?
An easy test would be to fly something faster, like the Darkstar, close to the ground.