Platform games with no lives often tend to break up the game into small, bite-sized chunks of action that require extremely precise execution. Platform games with lives tend to have longer levels that not only test the player's coordination, but also their endurance, and their ability to react to unforseen situations. In games with lives, your performance in one section can have a big impact on the next section- if you burn up most of your lives in the first level of the world, then you'll be walking on eggshells for the rest of the world. In games with no lives, each section is totally independent. Games with lives can feel more coherent, and have a more high-stakes feel due to the possibility of getting sent back a ways if you lose all your lives.
I prefer my platformers to have lives!
That's exactly my point. The mechanic makes you feel alert and makes you want to try it seroiously. Having unlimited lives really doesn't do any of that. It just makes you angry that you have to do the whole section again even if there are checkpoints and the player doesn't feel like learning a lot here.
