LUNA and UST are not equal, their rates of risk and reward of each one are distinct:
UST has no rewards because it trades it for more secure peg. LUNA, just the opposite, rewards in exchange of greater volatility risks.
Most of the value was attracted mostly for the stablecoin usecase. Most of the value of the project is still made up by the savings and users of the stablecoin.
It is not a coincidence that depositants are considered before shareholders at bank defaults. It is fairest, but also the best, if not the only, way to maximize the value.
Everybody may be equal, but in capability of voting the final proposal that saves Terra. Which, regarding the numbers, it would likely mean UST depositants would ultimately decide as being the largest mass of users. Maybe this is the ultimate reason why democracy is what survives: Because they are the one that wisely choose to prioritize the peg first and, thus, it is able to restore their systems when this happens.
Take a look at https://classic-agora.terra.money/t/terra-v2-upgrade/
cc @dokwon