Not filing a 501(c)3 because you don’t have to and why should you: a matter of prudence.
Making a big fuss over it, to the point of forming a new denomination, implicitly denigrating those who don’t: marketing.
Which new denomination has been founded?
Are you familiar with historic Baptist distinctives? They include the autonomy of the local church. Historically, Baptists didn't form denominations.
What are you refering to when you say that someone is "forming a new denomination"?