kshaw, "Welcome to the Forum!"
I'm surprised no one else has offered a "welcome" yet to a new member.
Ok, I understand your thoughts.
It's not a law,, but instead a range rule where you are to have a cased gun. In USPSA,, guns are required to be cased for transport from your vehicle, until they are in a safe area, where they are holstered. It's for safety.
But let's delve into your particular situation.
You've mounted a rail, and a red dot. Due to the number of various manufacturers of red dots, AND their shape,, it's very impractical for any manufacturer to try & build a case to fit all the variations. Besides,, they have no way of knowing what kind of red dot you may choose for your individual needs.
From the type like the Burris Fast Fire, to the UltraDot, to the Aimpoints,, all have very distinctly different shapes.
Ruger,, just like all other makers,, builds a case to fit the gun "As Built." When you customize it, adding a dot, a scope, a different set of grips, etc, you are changing the gun's profile.
Way too many variations for the original manufacturer to try & figure out how to build different cases to fit all variations.
A gun range likes to see cased guns as a safety measure. Fair enough.
For transport,, to & from a range,, you have been given some good ideas above.
As for storage, most of us who want our guns to stay in good shape,, do not use the factory boxes for storage either. Often, some cases can "rub" the guns when moved around,, and others,, especially foam lined ones,, can attract & keep moisture, which can damage a gun's finish. Many of us "old timers" have seen some rare and potentially valuable firearms ruined by long term storage in some cases. Foam, can have the ability to hold moisture. Any many fail to understand the fact that if you have a gun in your house,, and take it outside to your car & drive to a range, you went from around 72 degrees, to whatever the temperature is outdoors or in your car. The air has moisture, and it can & will condense inside a gun case, next to the metal. Left unchecked,, it can & will cause rust. Going from cool to hot, or warm to cold, & back & forth, is where this happens.
So, as suggested above,, you can get an inexpensive case, say from Harbor Freight, or other places,, cut out the profile you need for your gun, & use it to transport the gun. But for storage, after a shooting session, clean & wipe down the gun, but don't store it in the case.
A gun safe was mentioned,, and those are well worth the money. I can speak from personal experience. I had a home break-in several years ago, My safe kept the thug from getting a bunch of guns.
I hope this helps you understand why Ruger,, or for that matter, ALL manufacturers do not try & make their gun shipping cases "custom" for all variations of custom additions that are out there.