Why Data Warehouses Are Not Building Semantic Layers

Data warehouse vendors are looking into building semantic layer so Google board blue curve specifically for that right. So why it's not widely bought look or not doing this with some sort of you know like DDL? I just think my take is that DDL is not the best tool for the job for defining the metrics. Maybe there is some way you know like extending it, but it may look like if you extend it too much they're going to look like a look a mile instead.