I wonder how much that is based on the company background. Hetzner is a traditional hosting company. Cloud companies either had large existing software development base and datacenter expertise, being way larger than a company like Hetzner, (Amazon, Microsoft, Google) or don't run the hardware themselves (Heroku, various DBaaS offerings, ...) and focus on the software offering, typically backed by VC to cover the initial investment. I assume Hetzner would like to expand there, but it's expensive, a culture shift and somewhat risky given their well-founded and established competition.

EDIT: I guess DO, Linode, ... are closer equivalents to Hetzner?