No, but there's a lot of examples of "I don't have a better reason" regarding Apple decisions. I know that there's a lot of bad blood between Apple and Nvidia hence AMD GPUs every where before the M-series chips. Clearly, they are tired of of their cellular vendors, otherwise they would not have developed their own chips. But they already have the cellular relation for the iPhone/iPads, so what would extending that to allow MBP inclusion mean that makes it a non-starter for Apple?

I can only speculate. But my guess is that they don't anticipate additional mac sales if they were to ship this feature. So, the only reason to do this for them would be if it would bring in more revenue. And given the cost overhead related to patents that I outlined, it might just not be that interesting. My guess is that a lot of the agreements they have for this might cover iphones and ipads but not laptops.

It's not just Apple. 5G stacks in laptop are just very uncommon. Most vendors seem to independently come to the conclusion that they are better off not bundling that. Of course the difference is that Apple now has their own modems and chips for this. Which might change things but so far hasn't.

The reasons Apple want to vertically integrate everything and own it are easier to grasp: chips, firmware and software made by them are easier to control and upgrade by them. With qualcomm, they are basically getting them, their development teams, their supply chains for chips on the critical path to shipping products. And they are outsourcing what is a pretty major part of the whole phone experience to a third party.

Apple has been working on their own 5G modem for many years before they shipped it. I don't know for sure but I would not be surprised if efforts for that started when Steve Jobs was still alive even. This was always the logical move for them to make as soon as they got the idea of doing their own chipsets for their phones.