Because they should go when only the minority need to buy them, the majority able to do as the directive intended and reuse what they already have. The implementation coming when USB-C is relatively new is costing the average consumer, since as we all recognise, Apple et al were never going to drop the price when the accessories were removed.
USB-C came to Macbook in 2015, the iPad in 2018 (on the Pro, which means the majority of iPad users getting it for the first time between 2020-22 if they happened to upgrade at the point that USB-C came to their line) and the iPhone only last year, NEVER getting a brick in the box. Therefore only tech enthusiasts don’t lose out here - four generations of Pros (the average user probably does upgrade upgrade within that time, but don’t buy the Pro) two Airs, one Mini and one base iPad shipped with USB-C before the chargers were removed. Tech enthusiasts were also more likely to buy multiple sizes of devices while the chargers were still in the boxes.
Currently, it is tech enthusiasts with the spares/entirely unnecessary chargers since they make a free choice to buy a better one, and the average consumer having to pay for a means of charging when it was provided with the device before. Had the chargers been included long enough for the average consumer to upgrade from a USB-C device to a newer one, they too would be in the position of having everything they need for years to come. As it is, the balance is weighted more in favour of the environment/profits rather than a central position where the average consumer would never have used the charger even if it had been provided (the very definition of waste.)