They didn't have the ships or the men to do it. Remember, large parts of their army was busy with either invading or digging in on various islands throughout the pacific or fighting in China, and their merchant marine was busy keeping them supplied.
Well the DID have the ability, but it would have meant delaying the attacks on Philippines and the important East Indies.
Personally, I can come up with two scenarios where attack the West Coast would benefit Japan.
First off, and arguably the least likely, they could bomb the major industrial centres and harbours, taking away much of the US's construction capability and maybe more important in the early stages of the Pacific War, their refit capabilities.
That would have required a freakingly HUGE air campaign, Japan simply didnt have and could never have big enough airforce for it.
Another option was to sneak merchant vessels into WC harbours and sink them in strategic locations. The ships would pose as ships from other countries, in order to circumvent the US-Jap embargoes. They would enter the harbours just before the PH attack, preferably on the day and then scuttle in the immediate aftermath. Assuming it was done right, this could lock up harbours for months.
While i expect this could have worked, i doubt it would be "for months". Weeks yes probably but in the end the wrecks would either be floated away or simply blasted from the spot.
It's possible that if they had planned a massive follow-up land invasion, they might've actually been able to conquer some islands (Niihau, Kauai, Oahu, maybe more). A land invasion of these islands would've put Japanese forces right at our doorstep.
Doorstep? Unless you live on Hawaii, hardly, its a LONG way from the US west coast.
With any serious invasion they would probably have taken all of Hawaii rather quickly, as other clashes early on showed, it took quite a while for the allies to find ways to handle the Japanese shock tactics, which is another reason why this would have been impossible or very hard later in the war but quite realistic early on.
It's a scary thought, and I'm not entirely sure why they didn't give it a go before the element of surprise was completely lost.
East Indies oil was considered extremely more important combined with Japan aiming for a settled peacetreaty with USA as quickly as possible, meaning that actually taking any US held places beyond their "homesphere" was seen as far too provocative.
Quite stupid yes, and there were many opposing such though but they were overruled by those in power. And of course, its not like the Japanese were alone in such delusions. USA expected the war against the "obviously inferior japs" to be over in 6 months because clearly those primitive barbarians that couldnt even build their own modern ships and planes could never be more than a short term threat or fight on even terms...
And so on in different ways for USSR, UK and France who all had their own surprisingly stupid delusions about the coming war.