Why don’t women complement each other

I’ve got 9 sister in laws. Not one of them are graceful when it comes to compliments. I had them all over yesterday. They all came with their husbands and families. All together, we hosted about 50 of them. We made tons of food. Since they last visited, we got all new backyard furniture and I’ve turned my backyard into a gardeners oasis. I am very proud of my garden and go to extremes to keep it vibrant snd blooming. Not one compliment. Not one. Why? Meanwhile, I complement them on everything from their hair, their stories, their homes (when I visit). I feel like compliments are free so why not? Sometimes I even complement people just bc I know they would love one. Why are people so stingy?