According to an interview, I saw last year (possibly from Jorg), the reason this project (MSFS) exists is because technology that powers our computers, as well as things like AI and cloud computing has progressed to a point where Microsoft can finally build a true to life and realistic simulator.
We’ve seen this with Blackshark AI, the graphic fidelity of aircraft modals (graphics, not flight model), free world updates etc. As part of this Microsoft are aiming to include models and liveries into the base simulator.
Microsoft doesn’t want to get sued. An airline’s livery is part of their intellectual property (IP). In many if not most cases, they own their logos, their name, and the combination of their names, logos and colours.
I am definitely not a legal expert, so please note this is a lay opinion and is Not Legal Advice.
Copyright laws vary from jurisdiction, but generally speaking, you cannot profit from someone else’s IP without content. In the corporate world, content like this would usually require lots of paperwork and contracts.
Some airlines may want to fiercely limit the use of their IP, so groups distributing models/liveries without approval could face legal action (cease and desists, lawsuits, etc.)
Companies may also get upset if the theft of their IP results in a video that hurts their brand image. Imagine this hypothetical… Someone creates a livery for a real-world airline on one of their aircraft models. They publish it and someone uses that livery to make a YouTube video where they make a hoax video of a plane crashing into a famous building, or landmark. The video goes viral and suddenly, that airline could have a real PR problem, one that may cause them to seek compensation.
While a freeware developer is less likely to face legal action, both freeware and payware developers could. It is for this reason MS have to be careful.