Internet Marketing started becoming more complicated about 15 years ago when people realised that they could implement strategies that could help them get more visitors from search engines. Search Engines responded to this by becoming more complicated and less transparent so they were harder to manipulate.
As a full time internet marketing expert I can dedicate time to keeping on top of the latest strategies and changes that affect my clients. Someone who is not a specialist, such as your web designer may not be as up to date.
Some companies that “guarantee” number one spot within paid advertising. The number one spot is not guaranteed to be the most profitable when you consider the cost of getting there. Especially if they have allowed you (the client) to chose which keywords your site should be number one for instead of performing proper research into demand and competition.