Most economic assumptions are pushed for propaganda reasons. In physics you can assume the non-existence of friction and build a functioning model that approximates reality in certain situations. In economics, the existence of "perfect competition" or "perfect information" is simply fantastical, yet even at graduate level there are students building elaborate mathematical models with assumptions like these built in.
The reason these things are 'assumed' is clearly not because it builds simple models that approximate reality in any situation. There are no markets with perfect information nor competition. It does function to conceal sources of profit, though.
The reason these things are 'assumed' is clearly not because it builds simple models that approximate reality in any situation. There are no markets with perfect information nor competition. It does function to conceal sources of profit, though.