What is the rationale that explains why money should be taxed on each transaction?
Because we need to pay for communal goods that are more efficiently and fairly handled through government than through private transactions. We all benefit from having an educated workforce and voting pool, for example, so public schools make sense even if not everyone in them could or would pay for them individually; having clean food and effective drugs assured by a central body saves consumers massive amounts of time and money on having to deeply research each and every transaction (at a significant disparity of power relative to the manufacturers) to ensure that same thing.
That money has to come from somewhere, and no one is ever going to be happy about giving it up, so we have to find the least bad method.
Taxing profits (as we do with businesses) rather then revenues encourages businesses to succeed, then requires them to contribute back towards the things that helped them succeed - the roads that brought them customers and deliveries, the police that keep them safe, the schools that educate their employees, etc.
Taxing people progressively on income is the same principle. Those at the top, who benefit most from all the services of government (since they own businesses, have lots of educated employees, have lots to lose without strong policing, etc.) and who will be least harmed by paying the taxes are asked to do so.
Sales taxes should be abolished, since they're regressive and hit the poor harder proportionately than they do everyone else, but they're just another compromise for the sake of funding things we all want and need.
Estate taxes recognize that society benefits from everyone having to contribute things of value to the world before being encased in riches and luxury. Meanwhile, the son of a rich man is already going to have every advantage - the best schooling, trips abroad, top healthcare, business connections, etc. - and least needs a huge inheritance.
Plus, a high estate tax would get rich people to spend more money before dying, which can only be useful for the economy. You can't take it with you, after all. And hell, maybe it will be a boon to their souls! Rich people don't get into heaven.