Of course, the flip side of the coin is that if you do an UPDATE of a row in the presence of a secondary index, and the UPDATE doesn't touch the key, then you don't need to update the index(es) at all. So it really depends on how much you update rows versus how often you index-scan them IME.
[1] TPC-H doesn't have difficult enough queries to really stress the planner, so it mattered comparatively less there than in other OLAP work.