Why do I need to add a debit card to create an offer?
Let us answer this question with a question. Why would you want to sell your time and experience, your product, without any way to accept payment?
Symposium requires you to enter a debit card before creating an offer because that is how you get paid. All SymTalks and SymCasts are products you make available for purchase, and every one you Host results in a payment to you. The payments are transferred to your debit card unless you add a different account in Payment Settings.