Like built-in GPS, seat warmers and four-wheel drive, an amenity is a feature that contributes to comfort or value. Or in another sense, it's the overall pleasantness that results from all those cool features.
Declared the American novelist Edith Wharton, “I despair of the Republic! Such dreariness, such whining sallow women, such utter absence of the amenities, such crass food, crass manners, crass landscape! What a horror it is for a whole nation to be developing without the sense of beauty, and eating bananas for breakfast.” As you can see, people throughout time have gotten cranky when they’ve felt their amenities to be lacking.