Right now laws are openly available, but people don't care enough to get look into them. Also, just because you have "git blame" doesn't mean you'll now magically be able to see what corporate lobbyist wrote the law, because they'd just ask the legislator to commit it instead. Wouldn't change anything.
one big reason why people don't look at the laws is because they get changed all the time without a transparant way to see what ends up getting changed right before a vote. something like gitlaw would allow people, and lawyers, to track changes to laws much easier.
adoption is definitely the problem, but this can help lawyers make proposals and counterproposals with the speed of software developers, which may give lawyers a reason to sign on.