I can't say what the wooden bullet rounds were used for, probably several military applications such as use during combat training exercises and for various ceremonial purposes. As I mentioned earlier, several armies used V-B rifle grenades with wood bulleted rifle loads as propellants. But they were not used for shooting at the enemy.
Regarding U.S. .30 military ammunition (.30-40 Krag, .30-'03, and .30-'06), there were blank cartridges of several types made and used, but none using wooden bullets were adopted for general issue.There was considerable experimentation done at Frankford Arsenal on the development of wooden bulleted .30-'06 ammunition suitable for use in machine guns for training purposes, between 1912 and 1919. There were numerous wooden bullet cartridge designs developed and tested, but in the end, none were made in larger than developmental and evaluation quantities, and none were issued. The largest lot made was 100,000 rounds.