Front end developers love EAV tables because they can quickly built an interface that allows users to configure the properties of an entity (think a website that sells books and wine. One needs ISBN number, author, publisher, the other needs Vintage, Terroire, Grape, Acidity etc..)

But reporting on it is a nightmare as you effectively have to unpivot the data to use it and create very wide sparsely populated tables anyway and you have no idea how many columns you are going to need.