I don't see any merit in increasing amount of HBD in the system just to have more of it. Increase of debt limit means HBD has more room to grow organically before the haircut. By "organically" I mean as a means of payment for goods and services offered on Hive.

People are used to pay in fiat currencies, they have the intuition what price levels are acceptable and which are too expensive, merchants are also comfortable dealing with dollars, so HBD seems like an ideal coin to use in shops that want to offer their products for crypto but without volatility attributed to crypto. Hive with its social capabilities adds convenient way of communication with customers. That is a good environment for natural demand for HBD. But hitting hard cap sacrifices peg to dollar, which might spook the merchants. Increasing debt limit reduces such possibility even in case of heavy bear market, but the possibility increases with amount of HBD in the system. Therefore debt level being far from haircut level should be seen as positive thing, not an indication that HBD needs to become more popular.

We did hit hard cap relatively recently (a year ago), for a short time, soon after Hive-to-HBD conversion was introduced and people started using it. Thankfully the novelty usage died out and now we seem to be in a good place with debt level.