That depends a bit on the scale and use case specifics. But commoditized billion-scale vector search is indeed a thing. We published this for Weaviate in December last year https://weaviate.io/blog/sphere-dataset-in-weaviate
Embeddings for retrieval don't have to be. It is not unheard of to transform the raw embeddings to optimize them for retrieval; e.g., through binarization or hashing.
I was more making a distinction between embeddings and bag of words which are very very sparse matrices. The embedding dimensionality will not be anywhere near as high so this level of sparsity is a minor inconvenience.