Protestant cross-missionization exists for competition. Joe Blow reads the Bible, feels inspired, doesn't keep his zeal at the "humble" level and starts up yet another Protestant denomination. Nine times out of eight, Joe will claim that all those that do not listen to what he has to say are either wrong or damned with no chance of salvation. Joe spreads his ways to a community, studies them and then showers all with how the existing denomination of the area is wrong.
Long story short: another denomination that Christians everywhere may have to compete with at some time or another.
Orthodox cross-missionization exists for need. In the early days of the 20th century, people from somewhere, let's say Greeks, would arrive, send letters back home for a priest, priest would arrive, church would be built and everyone is happy. Different people arrive to the same place, let's say... Russians, and the same thing happens, but instead a Russian priest arrives instead of a Greek priest.
Long story short: people need to know what is being said. Same stuff, different language.
These days, the situation can be a bit more complicating. In Seattle, there is a ROCOR cathedral a block away from a Greek church. The same thing can be said in many other places, but with different jurisdictions. Maybe in the early 20th century parishes for different ethnicities were needed. These days, not so much which means that more cooperation between jurisdictions is needed.
Hopefully, whenever new Orthodox parishes are needed, there is cooperation and not competition. Cooperation would mean one parish where one parish is needed. Competition would mean multiple parishes where only one is needed.
Just my thoughts.