Why Is Allegheny County Sales Tax Collected For PA Residents?

County, municipal, and state taxes

You're required to charge county, municipal, and state taxes for regions your business has a physical presence in.  We're based in Pittsburgh, Allegheny County. So although you may be located in a county outside of Allegheny County, you pay the sales tax where Xgaming has a presence, not where you reside.

Pennsylvania is an ORIGIN-BASED sales tax state.
Pennsylvania’s Department of Revenue says on page 5 of their Retailer’s Information Guide, also known as Rev7-7

On taxable sales originating in a city or county that has imposed a local tax, a separate 1 or 2 percent local Sales and Use Tax is imposed.