Silver wire is used for some things, but it is a lot more expensive than copper which rules it out for most applications.
Here is a table of the conductivity (in units of 10^7 S/m), the density, and the cost of copper (Cu), aluminum (Al), silver (Ag), and gold (Au).
Cu Al Ag Au
Conductivity 5.96 3.5 6.3 4.1
g/cm^3 8.96 2.6 10.5 19.3
$/kg 9.03 1.2 1030 92100
If we had a copper wire with a specified capacity in amps, here is what aluminum, silver, and gold wires of the same length and capacity would weigh and cost as a percentage of the weight and cost of the copper wire, and what their diameter would be as a percentage of the diameter of the copper wire.
Weight Cost Diameter
Al 49 7 139
Ag 110 12646 97
Au 310 3190000 121
Cu is more conductive than Al so an Al wire has to have a cross section area about 1.56 times that of a Cu with the same current capacity.
But Cu is also denser than Al so the Al wire is only about 0.47 times the weight of the Cu wire.
Al is is much cheaper than Cu so the Al wire is only about 13% the cost of the Cu wire.