Hitting the green from over 120 metres out with solid iron contact is a great feeling. And you could experience it more regularly when your lie angle is correct. It’s also going to make it easier to control where you land on the green.
A stubborn slice could be caused by a lie angle that is too flat for you, rather than a swing issue. By correcting this, you can avoid unnecessary swing adjustments while hitting it straighter and more consistently.
Many brands try and solve the problems they think each golfer might have at different handicap levels by creating off-the-shelf irons with a specific lie angle. But that might not be right for you.