I'll explain it to you:
Rain, in amounts absorbed by the earth or handled by normal or routine collection is OK,
Rain that exceeds that amount is dangerous,
One of the things government is supposed to do is protect people. You know, police, firemen, etc. This costs money,
Government is big enough to do things for "the public good." So, costly things like lighthouses are maintained by the governments, not the private sector, which makes all decisions on profit & loss,
The funding requests come from experts who know all about "1000 year floods" and "worst case basis" and all that, plus an idea of what to expect for the next 20-40 years. They have the education and experience for this. Kind of like how civil engineers knew how to thick to make the walls of Tom Mueller Dam.
If for whatever reason this system of people and resources is interrupted, there can be problems.
When there are problems, like maybe someone's house flooding, people want to know why. The normal response would be to fix the problem, maybe one that shouldn't exist in the first place.
Let me know that you're tracking with all this and I'll continue.