As a first guess, one would think it makes more sense to eat 30% loss (so you need 1/0.7=143% installed capacity) than to need 200% capacity plus batteries since it's night about half the time on average. And afaik HVDC is more on the order of ~15% loss
Infrastructure (heck, just the conversion points alone are a huge part of the cost), but also regulatory hurdles like getting rights-of-way. Running an HVDC line is quite expensive; last time I saw the numbers crunched, it was basically impossible to make it work financially, no matter how efficient the lines were.
As a first guess, one would think it makes more sense to eat 30% loss (so you need 1/0.7=143% installed capacity) than to need 200% capacity plus batteries since it's night about half the time on average. And afaik HVDC is more on the order of ~15% loss