Why can’t I enter my own self employment expenses without upgrading to the self employment version?

The Deluxe and Premier online editions do not support Schedule C for self-employment expenses.  Only the TurboTax Self-Employed online edition can be used.

Or you can use any of the TurboTax desktop CD/Download editions as they all support Schedule C income and expense reporting - https://turbotax.intuit.com/personal-taxes/cd-download/

You can only self employment income into Deluxe or Premier.   To enter expenses you need to upgrade to Self Employed version .

Or you can switch to the Desktop Deluxe program.   All the Desktop programs have the same forms. You just get more help and guidance in the higher versions.  And Desktop has more features over Online.  If you want to switch post back.  We can tell you how.