Employment and consumer law tends to frown upon changing the body of law by contract. I'm referring to business formation, contracting, merging, fundraising, et cetera. If you sign under California law for many of these agreements, you will often find at least 3 pages listing out specific sections of California civil procedure and commercial code that both parties will, almost every time, find it beneficial to exempt themselves from. You can't do it in a single, blanket paragraph. You have to write out custom paragraphs for each and every section.

California may have a good body of law, but taking three to 4 times longer to litigate means it costs, cetris paribus, three to 4 times more to defend your contracts. That greatly benefits deep-pocketed litigants (and contract breachers).