I'm guessing the use cases they see don't involve query shapes that need to scan a lot of data. A columnstore along with vectorized or batched execution is a much better storage layout for fast scans with filters and aggregations (i.e., the top TPC-H and TPC-DS analytics benchmark results are from columnstore databases). A B-tree with tuple at a time execution is orders of magnitude slower [1][2].

[1] http://cidrdb.org/cidr2005/papers/P19.pdf [2] http://db.csail.mit.edu/projects/cstore/vldb.pdf