Sale & disposal of depreciable assets upon close of business

I sold or disposed of my business assets listed on Form 4797.  I also sold or disposed of other assets which were not listed.

1. It appears that the Form 4797 Line 18b sold assets were transferred as income to the Form 1040 Schedule 1 Part I Line 4. Then with business income or loss (Line 9), transferred to Form 1040, Line 7a. Why does this income from sale of business assets NOT go to Schedule C as business income?
2. Do I enter the sale of non-listed/non depreciated assets as Business Income on Schedule C line 1a.
3. Why is there a difference in how these sales are handled and where they are reported?

Thanks.