I live in San Francisco a major area for tech startups. I see Apple and many other tech companies advertising by billboard. As @steemdrive said it is supplementary to online advertising. A few years back I used to work at a restaurant as a waiter. There was a large patio that overlooked the downtown area. EVERYDAY I would get a perfect view of the Apple billboard and I own mac computers and an iphone. So who knows it doesn't hurt.