Veneers on a single arch are actually very common.
This is usually because most of the desired corrections are done in the more visible part of the mouth, which is usually the upper front teeth.
From a functional perspective, the front and incisal surfaces of the upper front teeth are not as heavily loaded during chewing as that of the lower front teeth. This is why most veneer cases usually do not include the lower incisors.
Also since the lower incisors are the smallest teeth in the mouth, this can make veneer preparation and fabrication challenging since the minimum thickness of porcelain required DOES NOT CHANGE regardless of the tooth being treated.
Other less invasive options for improving the lower front teeth can be some tooth alignment with braces/Invisalign and bleaching.