Thank you for your feedback. I understand where you are coming from. The devil is always in the detail.
Yes, you are correct, creating an economic value increases your personal net worth. If you call your net worth "capital" you theoretically credit it to your capital account. However, since we are talking about double-entry accounting, this would defeat the purpose of using double-entry accounting.
There is actually no difference between the creation of the art vs adding value to purchased material in form of art.
The double-entry accounting system was developed to obtain a transparent picture of the annual income and expenses broken down into categories and accounts. This is achieved by separating the accounts (general ledgers) between Balance Sheet (assets/liabilities - or items we own vs. to whom these items belong) and Profit and Loss Statement. (income/expenses)
When we close the books, we list all general ledgers in a Trial Balance. The summary of the debit equals logically the summary of the credits. Otherwise, you are in trouble.
At the end of an accounting period, we separate these general ledger balances between the Balance Sheet and Profit and Loss accounts. Logically, since we have allocated the accounts in the balanced Trial Balance to three categories, Asset - Liability - Profit and Loss the summaries of each category do no longer match. The difference between assets and liabilities equals the summary of the Profit and Loss accounts.
Therefore, by not crediting every single revenue/expense book-entry directly into "capital account", we have a summary of the profit achieved during that period broken down into details on an ongoing basis during the reporting period. When preparing the Financial Statement, we simply add the summary of all these Profit/Loss accounts to the capital account (equity) as a one-time one-sided entry as the "current month/year" profit to the capital. Now, all assets equal all liabilities and the current year's profit shown in the category "capital" of the Balance Sheet equals the summary of the P&L.
At the beginning of the next fiscal year, all Balance Sheet balances, (infinite) are carried forward into the next accounting period. The last year's profit is now included in the capital account as "retained earnings prior periods, and all P&L accounts (periodical) start from zero.