The Goverments fault
The type 45 is designed to have 4 Torpedoe tubes 2 x 4 Harpoon launchers and another 16 Vertical Launch Cells for a total of 64 designed with the space so they could be MK 41 VLS, and a towed sonar array. It was the govenment who didn't want to spend the money to buy the weapons.
Incidently Flight IIA Arleigh Burke also do not have towed sonar or harpoon launchers it was intended to develop an anti-ship which could be launched from the VLS they haven't yet developed one.
The first Arleigh Burke cost $1.1 billion, plus an additional $778 million for the ship's weapons systems back in the late 80s
Funnly enough with the problems the US is having with Arleigh Burke replacement the DG-1000 (which is itself the replacement for the cancelled DD21) $3.5 billion per ship and questioned anti-air capabilty are now buying more Arleigh Burkes instead.
Had we gone with the US route we would of probably signed up for the DD21 project and be in an even more of a problem now.