Why not consider an aluminium antenna instead? ...
Probably because it is illegal in the US to market
metal CB antennas, unless they have enough
insulation to withstand falling across a power line.
That’s why, for example, the CushCraft 10m Ringo is
“NOT FOR USE ON CB”, in spite of the fact that
it is tunable from 10m to 12m. Apparently some
Congress Critter’s cousin got electrocuted putting
up an antenna, and this was his revenge.
Of course, aluminum antennas will work just fine,
but antennas sold for CB market will often be
cheaper because it is a bigger market.