Actually the contrary is true. Each of those successful technical founders you just named did not "do the job themselves". In fact, you just named 3 pairs of co-founders(Google, Apple, Adobe) but for some reason excluded other key co-founders such as Allen(Microsoft) and the FB guys(https://www.facebook.com/press/info.php?founderbios).

Three variables that determine a start-up's success are its 1)product 2)market and 3)the team. Of these, the team is the most important. With a talented team, you can build, get feedback, and reiterate faster on your product. A team that can reiterate every week has a competitive advantage over the team can only reiterate every month because it can push a product out 52 times/year as opposed to only 12 times/year. A team with multiple A-players is always better than a team with just 1 A-player, and their products will be too.