I think pegging to usd was the demand of the masses because in usd terms it makes easier for them to remember how much they invested and how much return they can expect while pegging with btc seems a bit complex, personally i think pegging with usd is less profitable as compared to btc in the long term.
in terms of liquidity I agree with you as most persons are into cryptocurrency for profit/business.But this can also be archived (liquidity) if been begged to USD, BTC is not begged to Crypto yet it's has gained much liquidity, starting from the date of it birth.
What matters is the vision/mission of the project and it demands.