There is some regional pride involved, but the main motivation is the persistent meme from the Right that California's economy is going to the dogs because of their liberal policies, as demonstrated by the fleeing people and industries. This therefore proves that liberal policies destroy economies.
Particularly when "other factors" that may have little to nothing to do (directly) with actual regulation are what drove the business decisions resulting in said "flight."
A growing business deciding to build a multi-million dollar plant in another state because they offered either a tax write-off or tax exempt benefit that allowed them to come out a million dollars ahead vs the other offer isn't exactly a "regulatory failing," that was plain a simple bribery, just performed at a "non-personal" level(although the corporate decision makers will almost certainly see a percentage of it).
But bidding wars with tax payer money aside. Things that DO factor in:
1) Infrastructure,
1.a) Can the local power grid support what the business wants to do? (California has been hurting on this front for a while)
1.b) How "connected" is this location to transportation, either for movement of people(proximity to major airports, or direct access to several of them, not just one, is a major plus), or goods(freight)?
2) Regulatory environment relevant to the business being conducted, "cost of doing business" there vs elsewhere.
3) "Quality of life" for the skilled labor jobs.
3.a) Quality and condition of local schools.
3.b) Presence of other entertainment options in the community. Professional or College Sports? Museums? Theaters? Concert/performing arts venues and (regular concert) events? If you haven't had an "A" or "B" list performing artist stop by anywhere within 100 miles of your town in the past 20 years(while they were in their prime and still qualified as such), you're probably screwed.
3.c) Outdoor recreational opportunities in the area.
3.d) Cost of living. (Which can in turn loop back to the quality and condition of infrastructure, if quick/easy/reliable transportation can be had from a nearby low cost of living area, you're still golden, otherwise high costs of living presents problems.)
But, as Letterrip points out, this is a poor indicator of the effects of government policies. Regional differences are too great a factor. To compensate, the Right plays with the statistics, limiting the analysis to certain times when it appears to be true, making the problems sound worse than they are, and ignoring other comparisons (like Kansas).
Part of the problem is that in many cases, it is an apples and oranges comparison as well, and different parts of the nation are in various stages of either being apples or oranges. Policies that are good practices in regards to growing apples may be horrible when applied to oranges, and vice versa.
Republican policies in general, are good at generating growth in places where it may not happen otherwise, but the trade off is there often is little or no control to what is going on. So you get the infamous boom/bust cycle, and a lot of abuses often happen as a result of all stages of that cycle due to people who know how to take full advantage of each respective stage in that cycle.
Some Democratic policies are good at
controlling growth (after a fashion) by pulling back the throttle (by means of regulation) and thus slowing growth so that things don't collapse into chaos. The "problem" with the Democratic approach when taken to an extreme, is it creates an "unnatural" environment, that is wildly distorted from what it would be otherwise, and that distortion makes it VERY difficult to determine what is going on using any kind of direct measurement. As we cannot (as of yet) be completely certain that what we're seeing is the market behaving "as a proper market" or if its the market behaving in reaction to a (government) distorted input into the system.
California
seems to be "doing okay" based on direct measurement, but other (state) markets seem to be doing better in general, even if they aren't doing so right now. (trend vs instant) California also does seem to be nearing the point of needing to "pay the piper" for many of the promises it's made in the past, much as the United States Government is looking to be in danger of as well. Obviously, there are precedents for how a reckoning with the piper can be avoided, the US has done so in the past, but to do so, you have to grow you economy faster than your debt obligations grow.
While it's still possible, and even probable that the United States may be able to pull that off if it can get back on its historical track. The "trend" for California on the other hand says it's probably not going to be able to do so. Further compounding it for California is the matter that its "reckoning" will likely come long before the United States Government has its own meetup.