A good Funding Plan considers all forms of capital available for each stage of the business. As your company evolves, different forms of capital and investment types will make more sense for that stage of the business.
You can find yourself wasting a lot of time trying to leverage the wrong type of investment at the wrong stage of your business. If you're at the Idea Stage where you're still figuring out what your business might be, it probably doesn't make sense to be pitching Private Equity firms who only fund companies with significant revenue.
As your business evolves, you will migrate from simple forms of capital like credit cards and personal savings, to more complicated sources, like Angel Investors and Commercial Loans.