Although 10 seeds that are worse can make the playoffs over 7 seeds, they still have to win 2 games in a row whereas a 7 seed only needs to win 1 out of 2 games. On top of that, the 10 seed plays twice on the road and the 7 seed plays at home twice. If they are still not able to convert, this is their problem. Also, sometimes teams that are 10 seeds would have previously missed the playoffs but deserved to make it. For example, teams who lost their star players early in the year may have a crazy end of year comeback and be ninth in the west. Before, they would have missed the cut, but now they can make the playoffs and potentially make a run, which is more exciting.