In D&D, every character starts at the same age. Not the same chronological ages obviously but the same mental / developmental age. Whether dwarf, elf, half-orc or human, all characters start out as the equivalent of an 18 year old human school leaver about to start their first job. In short, everyone is created equal.
But not all game systems do this. In Traveller and Aftermath! characters started with radically different ages and abilities. In both cases it is possible for one character to start with three or four times the skills, abilities and equipment as another. This makes sense in the game environment. No government would allow an inexperienced 18 year to fly off in a multi-million credit spaceship on their own and in a post-apocalyptic world, those born before the ruin would be better educated than those born after it.
This game logic has unintended consequences. It gives players a huge motivation to cheat during character generation. The differences between the best and worse possible characters are massive. In D&D, a character with poor stats will be disadvantage but the gulf between them and a character with good stats is relatively small. A low Wisdom cleric still gets the same spell options, they simply cast less of them. A low strength fighter gets the same number of feats and starting money.
This cheating is not the mindless pursuit of power. It is need to make the game fun. A greenhorn character in a party of veterans will be left twiddling their thumbs as the more skilled characters exercise all their abilities, combat skills and knowledge. This is dull and frustrating for the players.
In Aftermath! or Traveller, the problem is compounded by poor experience systems. It is almost impossible for characters to develop in a meaningful way. There is no chance at all of a poor character coming anywhere the skill levels of their companions. This make long-term play of these systems unappealing unless the GM forces the characters to start at approximately the same age and experience.
These pondering on character age started because I watched all the of the Lord of the Rings films pretty much back-to-back (I’ve been ill). The Fellowship of the Ring is clearly a mixed ability party from the powerful wizard Gandalf down to the first level thieves Merry & Pippin. As the books / films progress, all the characters develop and gain new skills: E.g. Merry making a successful back-stab on the Lord of the Nazgul – What level has he reached to make that possible?
If your players had the Fellowship as characters, would those running Merry & Pippin get fed up with Gandalf and Strider doing everything?
Can any game system work when the party starts out with mixed abilities?