State Taxes: Why is There No Sales Tax for Products Delivered to California

I’m looking at furniture stores shipped to CA. My understanding is that if they don’t have a warehouse or office in CA, then there is no tax. What’s the reason for this? Because if I fly to the store in say Seattle and buy the furniture there, there is sales tax but when I ship it to CA, then there’s no sales tax.

State Taxes: Why is There No Sales Tax for Products Delivered to California