Well, Android tablets and phones are smart enough to play all apps from Google play.
However, socalled smart TV's are rather dumb, and only play a very limited number of apps from the site of their own maker (so Samsung TV's play a few Samsung apps, LG TV's play a few LG apps, and so on). Your observation is quite right.
How do I add the cw app to my smart tv? I have gone to google play in the browser and hit install but my device is t there for a selection. Also I know to view some apps but there very limited on the tv from what I saw. Is there something I'm not doing. How do I add google play as an app so I have more selection.