It costs money to mount a criminal case, and when government is cutting budgets for its investigators that makes it more difficult for them to do their jobs. Criminal cases also require that the government of the day supports your mission, and doesn't appoint foxes to guard the hen-house. The current head of ASIC hails from Goldman Sachs, and his father was - according to this article - a prominent member of the Liberal Party.
Of course, you also need laws that support your mission and provide you with the powers and range of punishments that your function requires. Laws that let you levy huge fines on institutions don't punish the institutions, but instead hurt the shareholders. Our regulators need to be able to bar certain people from working in particular industries - and pretty much everyone who has so far appeared at the Royal Commission should probably be on that list for the banking industry.
Of course they do! If the RC could look at the regulators, it would necessarily look very closely at recent government decisions. There is no way the government would survive that kind of probing. Let's see if the RC lasts long enough for a change of government, and if that in turn results in expanding the ToR.
I don't know how best to convey my sympathies to you, but... you're dreaming if you think any of the major parties is going to have the guts to make large businesses at all accountable for their crimes.
This certainly echoes my wishes, but again... how is an ex-politician going to get a cushy job once the public gets sick of them if they've made things tough for their future employment prospects?