Why does this always happen?

I left my Jeep at the shop yesterday with a list of about 8 things that need to be checked or done. (It's rolling over to 100,000 miles). Now, for those of you who have ridden in my Jeep, you all have heard and commented on the horrible, grinding noise it makes when I make turns. Guess what? yep, the guys at the shop drove it around for 20 minutes and "ma'am, we never heard a noise." URGH!!! It makes a horrible noise!! I promise! But nope, not making it today when it really needs to! Why does that always happen? So, the men think the woman is nuts!