Physical Theray Needed? Late Walker?

My son is 14 months old. Currently he isn't walking yet. He will walk all day if he has ahold of your 2 fingers and he cruises around holding on to furniture and such. He just hasn't taken the step to let go and do it on his own. His doctor said at his 1 year visit that if he wasn't walking by his 15 month appointment, she would send him to PT. Well, it's in less than 3 weeks. Is that really neccessary? From what I've read, it can be normal to walk later. Or is my son behind? Should I be worried? I really don't see anything wrong.