One of the reasons why Ellery doesn't have a "big fancy place" or big multi-bedroom rancher is because of his relatively stoic lifestyle. Sparsely furnished, for a man who had planned to be alone after finally giving up following the breakup with Bill. He isn't very materialistic, and so his home reflects this simplicity. That was the thinking behind the "carport" rather than "garage" concept.
It does snow 11 months of the year in Wyoming, largely due to the mountain effects, but Laramie is in the southeast, out of the high mountainous terrain. Hard to say whether it is "realistic" or not for him to have a carport, now that I think of it.