Yes, it has absolutely nothing to do with taxes. In fact, in some state like Virginia (when I last investigated this) you have to pay extra to the state for an out of state incorporation.
The key is not so much "friendly to corporations" (that gets complicated, especially when corporations sue each other) but I might say as "sane, stable and speedy" (I think, for the latter; at the very least they have a separate Court of Chancery that handles an important subset of corporate issues). This is a big business for the state government (1/5 of state government revenue) and the associated firms that do their part and they do their best to keep things on track and be efficient (I used to work for a company that sold one or more high speed Kodak ImageLink scanners to the state in the early '90s).
The case law you cite speaks to the stability concern. Companies aren't so much interested in "friendly" as they are in "a known quantity". When the rules of the game are stable, you can plan with some degree of confidence.
