They could, and they should.Instead if sending your ship to sit there for a long fucking time, you could sent it from the port of exit, to Panama, then to the east coast (Southern)
But that would cost fuel and canal transit fees.
And from the rumors I've been hearing about the backlog and the motivations of the large shipping companies...their upper management/owners are making a killing on container prices and ship slot priority.
So they are not really terribly interested in speeding things up or clearing up the problems in the supply chain, as long as the backlog and maritime traffic jam help thier personal profit margins.