There's a lot of politicking in the Pentagon, Congress and even in the Department of Defense's civilians. You cannot assume it is purely a technical problem. During the Clinton administration, lasers were largely verboten. They were a legacy of SDI and, therefore, bad. During the Bush administration, Rumsfeld was not a fan and wanted his FCS + fought two wars. During the Obama administration, they were neglected at first and then started getting more funding towards the end, but even so there were how many wars?
Laser development has to compete with other priorities in the Pentagon.
After all, this is the Pentagon that thought the Littoral Combat Ship was a good idea.