Ask HN: What does the software industry without patents REALLY look like?

Keep in mind, we have an example of a software industry where patent use is virtually non-existent - HFT and quantitative finance almost exclusively use tight confidentiality and trade secrets to operate.

Without patents, do new compression algorithms, data structures, etc stay trade secrets only to be used in situations where they can be protected?

Not defending just making a probing question at a weak spot of the argument that I haven't seen seriously confronted.