It’s certainly true that automatics are far more common than manual cars these days. It all started decades ago when people decided it was easier to have the car shift gears for itself than bother to shift them manually. But there have been other factors, too. One is that modern automatics no longer represent the performance shortfall they once did.
Back in the bad old days, autos used to be less efficient than a manual, leading to less acceleration and greater fuel use, making the manual the natural choice for a keener driver. But modern automatics have really caught up and no longer hinder performance or increase thirst. In fact, the best of them can shift faster than a human ever could and, with eight, nine or even 10 ratios, they can be more efficient than a manual.
Turbocharged engines have also helped make the case for automatics and – generally speaking – turbo-motors often work best with an automatic where there’s no lengthy gear-change interval to allow the engine to fall of boost. And turbo-diesels which need boost to operate and don’t rev very hard in the first place, are a natural choice for an automatic which also works very well for towing and when driving off-road.
But there will always be people who prefer manuals (yours truly included) especially those who actually enjoy the physical aspects of driving a car. So while the manual transmission in your car will turn some people off, if you can find the buyer who wants a manual, you might find the rarity of your manual car will actually be a selling point.