It's not about lawyers cutting a good deal for themselves. Liability issues get complicated along multiple dimensions when they involve licensed professionals, even when they're day-to-day working relationship is indistinguishable from any other employee. And lawyers, even more than doctors, are at the furthest extreme of this complication spectrum. Even were software engineering to become a mandatorily licensed profession like some other engineering disciplines, there's little reason to believe insurance products would mirror those in the legal profession. I seriously doubt we'd end up in a place where employers are common--let alone routinely--paying to cover liability for work outside the scope of employment.