Why does this game stretch to widescreen?

[Melon]

Honestly not necessarily a complaint nor am I asking for a fix but like, Why? For a game made in 2014, you'd think the game wouldn't have this issue of either being stretched into 16:9 or playing in a small window without an adjustable resolution.

Again, not even really a complaint. I've seen it so much at that this point it looks MORE weird not stretched into widescreen, but still. Why?