You’re using a tilted and flattened map. Look at the US on Google Earth. It’s not level with latitude lines, and the northern states are expanded on any flat representation.
This is most noticeable at the equator, where there is no large variation. (There’s about 8 minutes difference due to secondary things, not axial tilt.)
Sioux Falls SD is 43.5460°N
Rapid City SD is 44.0805°N
Sioux Falls Sunset is at 5:13pm CST
Rapid City Sunset is at 4:38pm MST
If both cities were in CST, Rapid City sun would set at 5:38pm CST
Due to the latitude difference, the sunsets should be 25 minutes apart
However, they are 35 minutes apart due to the time zone difference
If you said “Sioux Falls is farther south than Rapid City” and tried to base sunset time on just that, you’d be wrong.
And? We’re not abolishing timezones any time soon. So there’s always going to be that issue of the easternmost and westernmost towns in a time zone. That’s not a reason for anything.
… do you believe the person made the image for this comment? What evidence is shown in the image for you to believe that the tilt and shape of the earth wasn’t taken into consideration for the graphic, besides it being shown as a 2d image?
Because the reasons for the varying lengths of day are well known It’s more an exercise in figuring out why the map has such slanting in it.