DC is harder to turn off safely. A high current contactor will arc under both AC and DC - but an AC arc tends to be self extinguishing. Solid state switching is less efficient and requires power to activate. They also tend to go up in flames when they fail.
HVDC is used only for long distance transmission, where the capacitive load for AC systems becomes a major source of loss. The only other time it makes sense is when the current required is so high, the skin effect at AC frequencies results in cables that need to be substantially larger. In cases like that, though, it's often easier to go with multiple smaller cables anyway.
AC is demonstrably easier to engineer around, and safer as a whole. There are some good arguments to be made that DC might be safer under some circumstances should you become part of the circuit - but the whole idea is that people should not become part of the circuit in the first place, so that's a non-issue.
Also, regulating DC to various voltages just means it converts it to AC first then back to DC... unless you're using linear regulators in which case the unneeded power is dumped as heat!