Why is the default TAX or Drop Down choice [blank] in Zoho Books ?

Why is the default TAX or Drop Down choice [blank] in Zoho Books ?

I noticed every time I categorise an expense I must manually select my tax from a drop down list.  If ZOHO was created in a tax free haven that would make sense.  I have missed to charge GST on invoices and missed out on claims on purchases.
Why is the default tax choice [blank]  It would be better if a user could select a preference of what the drop down list displays. Or just set it to the default TAX most of us need to account for.