It isn't as simple as 'just send the ships to the East coast instead.'
Even discounting the costs of travelling that far, those cargoes are being sent to western ports for a reason. There's an entire logistical distribution infrastructure that they're already plugged into and planning on using to move those goods once they're off the boat.
In order to do it on the East coast instead, they'd need to both break contracts with those already involved in distribution, and make new contracts with other groups. They'd need to plan, implement, and correct entirely new networks of logistics, or if they're already large enough of a company to be operating from both ends, radically rework the networks they already have in place.
If they have to wait a week to unload at LA/Long Beach, everything still works through the estalbished channels and patterns, just later and slower.
If they have to unload at the East coast, some of their cargo would then have to be shipped all the way back across the USA to California, etc.
If things get bad enough, they'll start changing what they're sending on what boats so that some traffic can be diverted to the East coast, but if a ship is already packed with cargo intended for the West coast, it's incredibly complicated and more than just some fuel and transit fees to get cargo handled through different ports.