I went on a Realtor tour yesterday and the one glaring complaint I had about over half the homes was weeds and lack of care to your grass. Your lawn sets the tone for the entire showing. If its overgrow with weeds and brown that suttley suggests to the potential buyers that you do not keep up with your home's maintenance. If its green and lush and mowed, it suggests to your buyer's that you were able to keep up with your home's maintenance.
When showing homes and the yard isn't mowed 9/10 times we may as well leave the property immediately. Yes the buyer's are that turned off by thinking of the time investment to relandscape.
Just remember the outside appearance is just as important if not more important than the inside appearance.