When it comes to early-stage companies, skipping venture capital stages happens very rarely. The reason for all the different stages of funding is to minimize risk for all parties involved while setting milestones along the way. Companies aim to raise as little money as possible to avoid dilution, but enough for them to grow their business and achieve their long-term goals.
In most cases, companies that skip funding rounds (venture capital stages) have either (a) bootstrapped their way out of the seed round, or (b) achieved most of their targets with seed money to be able to skip series A. The first one happens quite often; the second one is the goal of every startup founder.