Break it down...internet, not. Shopping...not (you haven't hit the "purchase" button) Internet shopping =>purchase...calculate the tax.
Also, just consider how many local tax jurisdictions there are in this country...and then put yourself in the place of the folks who have to implement all those various rates into their "back office" software...and then, keep it current.
As Maggie Thatcher said,"The problem with socialism is that you eventually run out of other people's money." Do this interesting exercise...calculate all the taxes (local, state, federal) you pay on all your purchases for one month. Multiply that by 12 to get a sense of what you're paying every year. THEN, add to that your property taxes, all the money automatically deducted from your paycheck for various taxes for the year. Then, realize that you get to keep the left-overs...so as to buy a home, buy a car, put a kid through college, put clothes on your back, etc.
I have a dream that any and all election days have been moved to April 16. Think of what April 15 is. I'll bet campaigns and political posturing would take on an entirely new face if candidates had to face the voters the day after the voters have filed their income taxes. As it is, we pay taxes in April and then vote in November --nearly an 8- month difference. Just a dream, I know...sigh.