Nothing scales right at 1440p. 1080p was standard for so long that everything was made for it. Then 1440p comes along, 33.3333333333333333333...% bigger and it cant scale, so everything ends up bigger or smaller than intended.

4K is at least 100% bigger, so its just a better definition 1080p.
For games, there's no reason we cant have 4K and high framerates with current hardware, well... except for money, publishers/developers dont want to spend the time.