Because if we didn't have a strong government, this world be be chaos. Nothing would EVER get done. A weak government wouldn't do anything, I think that there would be more wars, more everything.
The answer really depends on what you think of as a "stronger" government. However, in order for a country to be stable and ensure that their citizens can thrive, and thus survive, needs to at least provide it's people with health, living conditions and economic opportunities. All of these things cost money, which countries get from various economic activities, but usually from exploiting natural resources. So say in a country there are natural resources, such as oil, the oil is exploited and the government gets a cut from the profits, which it has to reinvest to ensure it's people thrive and survive. A strong government ensures that no foreign country can take advantage of the resource, that it will be exploited responsibly and there will be no corruption in the use of the money, therefore guaranteeing the country's survival
But in modern times, as we see, Wakanda is a thriving, flourishing civilization with few conflicts with the outside world. So the primary function of challenge day is keeping the peace internally, with making sure the Black Panther is a fit protector now a secondary outcome. And there for it was kept a hidden for a while.
