There are numerous bots that perform arbitrage and perhaps other sorts of automated trading between the internal and external markets. HDB stabilizer continually (as long as HBD is >$1) sells HBD, often to bots, in order to buy HIVE, often from bots. Those bots then go and perform the offsetting trades (i.e. buying HIVE and selling HBD) on external exchanges. So it is inducing both HIVE demand and activity both internally and externally.