HVDC is used for long-distance transmission where taps aren't necessary, and to connect disparate AC standards. Popular applications are undersea cables, remote generation facilities, and intercontinental or inter-country distribution. It's a lot more efficient than AC over distance as it requires fewer conductors and doesn't suffer from skin effect, so transmission losses are lower. And since you're already doing the AC->DC->AC conversion, there's no need for the connected grids to be synchronized.

As renewables (solar, wind, hydro) become more popular, so too does the need for reliable long-distance power transmission. With fossil fuel, fuels could be delivered to the point of generation - with solar, wind, and hydro, the location of the generator is non-negotiable and so the energy must be transported instead.

So we'll probably see more and more HVDC systems in coming years.