For Mercedes, I cannot make a rationale comment because I don't know much about their demographic.
For Ford and GM, it's simple. The macro market demands big vehicles with ICE drivetrains. Why invest huge money in a reasonably small EV market niche when they can pump out trucks/suvs which command good profit margins with existing resources (engineering, development, production) already in place? Mass market EV acceptance is way off in the future. It doesn't make sense to forego the big money on the table now for the "what if ..." possibilities of the future.
The Big Three have always focused on the present and not so much deep into the future. I'm not saying it's right or wrong; it's just the way they are.