Instead of trying to tax purely digital activities, why not just raise the income/property taxes on the people who live or work in your city? This would be a lot less regressive, and would prevent people from getting around it just by changing their credit card billing address. Not to mention the beauracratic nightmare of requiring SaaS companies to keep track of every customer's physical address and local tax regula…
Because raising progressive taxes that are already high make it likely you’ll trigger a death spiral where high earners flee, raising the taxes you need to levy on the rest, etc.
If people could see the some total of the various taxes they pay, they'd be shocked. I'd love it if Stripe or other payment processors started reporting taxes to credit card companies so we could see the total sales and other taxes we paid across all transactions on top of our income taxes.