You are confusing two things.
A non immigrant has to demonstrate they have ties to their home country and that might include financial ties such as a job, or a home they own etc. They might also be asked to show they can afford to pay for themselves whilst in the USA, but that is more a border check thing.
An immigrant (ANY immigration case) has to address the applicants ability to support themselves in the USA. For Employment based (EB) cases, the job covers that. For Family based (FB) , someone has to fill out an I864. For DV based applicants (where there is no third party "sponsor" as there is in EB/FB cases) the applicant is supposed to demonstrate their own ability to support themselves, and that is sometimes done by financial statements, or I134.