The building code is a MINIMUM requirement, not a bible. You can go as far as you want to but most people build to the minimum to keep costs down.
For example, before double-glazing was mandatory, you could still use it if you wanted to. Most didn't because the code did not require it and it costs more. I know people who opted to use it before the changes because they thought long term.
When building there are two costs to consider. The capital cost of the build process and then the running cost of the structure for it's life. The capital cost is a one-off but the running cost is ongoing and increasing. Most people focus on the capital cost and try to minimise it at the expense of the much greater running cost.
When I built my house almost 18 years ago I used a 12mm bandsawn finish ply for the cladding. It was a little unusual around here at that time but I saw benefits in it given the periodic winds we can have. Made mistakes in the build too simply because I didn't know enough, things like lack of thermal mass and I should have opted for 150mm walls instead of 100mm to get better insulation.
Live and learn!
