I've had about 25% of my reviews being 4 stars and, of those, 90% were for ridiculous reasons. The 10% that were not, I paid close attention to the issues which were raised and tried to correct them. But for the others, I've come to the conclusion that some people just will not be happy no matter what they are provided and that there is little point arguing with them about why they gave only 4 stars.
Some people will say things like "it wasn't a hotel" or book the room, knowing full well the location and proximity to the city, then mark the rating down that the location was not good. I actually just had a pair of women from Germany, who I even offered to go and pick up their take-out for them at a local restaurant, and asked them several times (in German) if they needed anything else for their stay. They acted very nice, said everything was wonderful and then- four stars in every category, one category a three star, and four overall.
I have to remind myself these are strangers who I know for only two, maybe three days at a time, and there is no telling what they are really thinking.