It would be like getting married just so you can go on a couples cruise... or marriage counseling... or something...
Maybe an incubator would be helpful for your startup--let's assign some probability to that. There's also a probability associated with your startup succeeding without an incubator.
Having the right cofounder will likely increase your odds on both sides. However, having the wrong cofounder will nearly guarantee misery and failure. Just as in marriage, rushing into it will greatly increase your odds of missing something and picking the wrong person. There are always exceptions (love at first sight) but consider the odds rather than the exceptions.
So no, don't do it just because incubators tell you to. The history of enterprise is filled with businesses that did just fine without incubators.