A gas kiln fires by burning fuel in the chamber, which lets the potter starve it of oxygen and force a reduction atmosphere. That single capability is why gas kilns persist despite being harder to site, harder to run and less convenient than electric ones in every other respect.
What reduction does
When the kiln is short of oxygen, the burning fuel takes it from the materials in the glaze and body instead. Iron shifts towards green and grey, giving true celadons; copper can give red; shino glazes carbon trap; and bodies develop the flashing and speckle that reduction firing is loved for. None of this is available from an electric kiln at any price.
What a gas kiln needs
A flue, a properly considered location that is almost always outdoors or in a purpose-built kiln room, a gas supply or bottles, and considerably more attention during a firing than an electric kiln. Firings are managed rather than programmed, with the potter adjusting burners and dampers to hold reduction at the right stages.
Why most studios stay electric
Siting. A domestic garage or spare room accommodates an electric kiln and does not accommodate a gas one, and most people's constraint is the building rather than the ambition. Community and shared studios are where most potters get access to reduction firing, and hiring space in one is far cheaper than building a kiln shed.
Getting reduction effects without one
Commercial glazes formulated for oxidation reach convincing versions of many reduction colours using different colourants. Raku gives its own post-firing reduction outdoors in a bin. Neither is the same as a reduction firing, and for a lot of work the difference matters less than the availability.
Questions people ask about gas kiln
What is the point of a gas kiln?
Reduction firing, which changes what iron and copper glazes do and is not achievable in an electric kiln.
Can I have a gas kiln at home?
Only with a suitable outdoor location or purpose-built kiln room, a flue and a gas supply. Siting is what stops most people rather than cost.
Can I get reduction colours in an electric kiln?
Commercial oxidation glazes reach convincing versions of many of them using other colourants, and raku gives its own reduction outside the kiln.