Really wasn't part of the whole deal with the Reagan administration reorganizing the Division of Highways to begin with?...because they had a lot of plans and built a lot of miles of road that probably wasn't necessary? It might not seem like it nowadays with almost 40 million people here in California but most of these roads and especially the expressways were built in an era where they would have seemed almost like something out of FritzOwl thread. Really there is very few places in this country where you will see state highways or even US Routes built to the configuration and standards they are here in California.
The sad thing about improving infrastructure is that sooner or later it makes myopia look like a plausible electoral choice. California has about 13,000 miles of state highway, of which about 5,000 is freeway of one type or another, and the trend of California doubling in population every 20 years had been established in 1870 and was in full swing during Reagan's governorship.
California had about 20 million people when Reagan left the governorship in 1975, so there were then about 4,000 people per mile of freeway. Now there are 8,000. In comparison, Kansas has had much slower population growth and a more measured approach toward development of its state highway system (capital investment increased modestly above an early-1980's baseline for three decades). The state highway system has 10,000 miles, of which about 1100 is full freeway (874.34 miles of which is Interstate), which works out to about 2,700 people per mile of freeway. In spite of this gradual approach and the clear benefit of the three decades' worth of investment (visible not just on the freeways--about 30% of the current mileage opened in the last 30 years--but also on highly improved two-lane state highways), however, we now have a conservative Republican governor who steals from KDOT on the premise that "the state highways are in pretty good shape."
So the question is this, what is necessary and what isn't? Really with all the routes over the Sierras today it would be incredibly hard to argue that another one should be built or would offer some sort alternative to get people moving faster than what is already in place. So all that leaves left is a simple aspect of accentuation, but is there another Tioga Pass or Sherman Pass in the protected lands worth investing in?...possibly but probably not likely.
I have visited Devil's Postpile National Monument (though not during the season when shuttle buses must be used), so I have had an opportunity to appreciate the potential convenience of a denser ladder of Sierra crossings. I was bound for Manzanar and Death Valley as part of the same trip, so I was not planning to get directly from Mammoth Lakes to Fresno or even Merced, but I was still very aware of the Sierras as an impenetrable wall at that point. However, I don't think I would sacrifice this part of the Sierras for an easier crossing, especially when the major population centers outside the San Joaquin Valley are better served by the routes that already exist, are highly improved, and are maintained fit for travel throughout the winter.