OK, that was an extreme and ridiculous, but imagine how a slew of subtle differences in laws could create difficulties between unsuspecting citizens?
Look at any relativity free market. Are you overwhelmed by incompatibilities? Most video connections are HDMI these days. Most gadgets take AA or AAA batteries. Most cell phones use mini USB to chargel. Most cameras use SD memory cards. Most cars have CD players. I could go on and on. There aren't government regulations that force any of this to happen. Businesses want to make money and while there is money to be made in variety, that only goes so far and only when it makes sense. If people want standardized laws, they will get it. If people want different laws but to be able to know when those laws apply, they will get that too. Someone could make a GPS device that detects your location and shows the laws that apply in that area depending on which court system you subscribe to or whatever. Don't underestimate how smart people can be when they are acting out of their own selfish interest to obtain wealth.