I could arrange that!
You could? Cool!
In that case I will relegate all the business decisions that need to be made to you, and my job will purely consist of the very important task of deciding in what assets the company invests in and who is going to take care of them. That's a very important job after all, and I will probably have no time for anything else.
Ok, here you go coming down on my brilliant ideas, again.
Well, it wasn't that brilliant because 'wealth' is not something that can be easily measured in one way or another. If you tax only one way to define wealth, all the rest will be just one gaping hole in the taxsystem. If you define wealth as the number of dollars someone has, they will trade in their dollars for something else. If you define it by the number of cows, people will instead buy donkeys. People already put their homes on the name of their firms or on the name of members of the family to avoid taxes.
That's the real reason taxes are complicated. Some people try to avoid them and others try to get as much of it as they can. They end up in an evolutionary arms race, with one making things more complicated for the other. It's a bit like a snake needing to become more venomous to be able to kill a rodent, that becomes increasingly more resistent to the venom of the snake. You can decide for yourself who is snake and who rodent.
Of course in such an arms race, only individual battles are won. On both sides more and more energy is needed to just maintain the status quo. None of the sides can just decide it doesn't want to play anymore. In the government versus tax-evader battle, it means that the complexity of the system is only going to grow. It's 9000 pages now. Don't bet on that it will be fewer in the future.
Another reason I suspect why taxsystems are so incredibly complex is because of the politicians constantly promising to make it simpler. Trying to simplify something that is inherently complex, is not easy. Whatever plans they have, those will have to be changed. There will have to be exceptions to the rules, and rules ruling the exceptions. Everytime anyone wants to simplify things, they will be adding another layer of complexity. It is easy to shout some simple idea you think it should be based on, getting it implimented in a way that is actually going to work and doesn't hurt so many people that they will protest, or make it too easy to avoid it is a very different matter.
The people who are constantly demanding that taxes should be simplified, should also ask themselves whether they want things to be simplified for the taxpayers or making it run on a smaller bureaucracy. The two things don't always go hand in hand: the assembler programming language is very simple and runs on simple computers, but on the user side it is not easy getting anything done. Windows is very bloated and complex, but for the user it is much easier. Similarly, making it easier for the average taxpayer to calculate their taxes does not necessarily mean the bureaucracy to make it simpler for him will be smaller. I suspect quite the opposite.