Freshly sharpened blades make for beautiful cuts.
I first found out when I was younger the hard way about dull blades need to be sharpened or replaced on lawn mowers if you want a nice flush cut with nice lines and straight edges. If you cut grass for a living or just to maintain your own yard you have probably already had to do this more than once. I prefer to sharpen my blades with a bench grinder about every 2 months. New blades aren't as sharp as when you do it yourself. Just make sure to use a mower blade balancer or pliers to make sure blade weight is balanced on both sides of blade before mounting back on lawn mower. It only takes minutes to sharpen and saves money.