Well, Microsoft did try really hard, it was called "continuum", but the fall of windows mobile brought that dream to an end. The other company that tried was U

Well, Microsoft did try really hard, it was called "continuum", but the fall of windows mobile brought that dream to an end. The other company that tried was Ubuntu, their effort was called Unity if I'm correct. That was axed recently as they needed to focus on profit-making parts of the company. Also, I don't think any mainstream ubuntu phone with unity was ever released. Finally, Apple's strategy is clearly different, they see iOS and macOS as clearly different beasts, and will probably never try to directly merge the two. Data-sharing is the way to go for them.