it seems like they mostly are putting force powers on characters that use them as a major part of their identity. Characters like Kyle and Corran used force powers eventually, but they were already good at what they did long before they ever started using the force.
you can make other arguments based on force-using character distribution across factions or potential game balance issues if certain pilots had access to force upgrades or whatever, but I think from the designers' perspective (and possibly Disney) the intent of keeping the list down to just the essentials is all there really is to it.