If Urza is an artifact he gets all bonus for being one, gains his own menace making it easier to do Commander damage to opponent with him
They can either print cards on the same power-level with more complicated and niche effects with restrictions, or simply make new cards more powerful than the old ones
We often share pop cultural and mythological backgrounds, so the same things get to many of us, which is why I think my top five will likely mostly hit for everyone
So if you leave him unexerted, your opponents will have a hard time getting rid of him
For example, a first edition Blastoise was famously rejected by PSA because someone used a blue marker to fill in nicks on the back of the card
Some cards in other sets refer to a card, spell, or permanent that "has an Adventure." This refers to a card, spell, or permanent that has an adventurer card's set of alternative characteristics, even if they're not being used and even if that card was never cast as an Adventure