Doesn't every state have similar laws? Indiana does - yet I don't normally pay sales tax online, because most of the companies aren't based in Indiana, whereas online companies really do tend to be in California.
Lots of states, but not every state. California is also of particular importance because it's so big: nobody would care as much if Delaware had laws like this.
However, in California, even if you only have a physical presence in some remote part of northern CA, suddenly that affects your ability to sell to 37 million other people.
However, in California, even if you only have a physical presence in some remote part of northern CA, suddenly that affects your ability to sell to 37 million other people.