They tried to reflect the actual letters used in the original script, and differentiation between them. Same reason the Thai place Phuket had a silent h after t

They tried to reflect the actual letters used in the original script, and differentiation between them. Same reason the Thai place Phuket had a silent h after the P - romanisation of ภ to differentiate from พ, ผ, ป, and บ, albeit the last two are pb.