<i>...if this is such a great idea, why didnt the legislature just vote it in?</i>

iirc, the structure of the use tax was set by a vote of the people as the structure is set in the state Constitution. Remember Engler's math double talk where he was promising a big property tax cut, in exchange for "only 2% increase in sales tax"? What the sales tax increase was was 2 percentage points, ie a 50% increase in tax rate, but he was depending on voters not being able to do the math.

Prop 1 restructures the use tax again, so that means it has to be approved by voters just like the increase from 4% to 6%.

Another thing thrown in is a prohibition on the money shuffling authority increasing taxes and a prohibition on an increase in use tax rate. The Authority doesn't have authority to raise taxes anyway, and an increase in the use tax rate would require another vote of the people, so those provisions have no function other than to get support from the people who blindly vote against any tax, any time, for any reason.