One aspect of character progression, which has been unfairly maligned by those who don't understand it, is that new characters should start at level one. When characters progress visibly through play, and death means losing all of that progress, players will become even more invested in their own characters. Player investment in their characters is one of the most important aspects of an RPG, so this is generally beneficial to the game as a whole.It has been suggested that progression, or the lack of it, is the main reason why D&D was more successful than those other systems.
Ever since 3E or so, there has been a type of player which is obsessed with power and optimization, such that they don't care if they die because they relish the opportunity of bringing in a new character that is freshly-optimized for their current level. They don't care about the character, as much as they care about what that character can do mechanically. Requiring new characters to come in at level one is usually sufficient incentive to prevent them from meaningless sacrifices in the name of power.