> The only downside of later optimization is that in commercial environment they often don't let you clean up.

Exactly (speaking for custom industrial automation projects). The follow up next requirements for a project might be in 5 or 7 years or never. You would be cleaning up a 80% dead project. In these environments, it's not uncommon to no longer have a dev environment because the system is a singular testbench that costs upwards of 2 million and only exists in 2 factories, so all bugfixes must be extremely conservative and any refactoring is stricly forbidden because there's no way to locally test for regressions.