You know that feeling when you get a phone call from a random company trying to sell you something you did not sign up for? Well that is exactly how people feel when you interrupt their day with your product or services without their permission.
Wouldn't you prefer if your prospects gave you their contact details themselves because they showed an interest in what you're offering? That is exactly what lead generation is all about.
This is a form of marketing popularly known as inbound marketing where your prospects are targeted online using digital Ads with a Call To Action.